JP2644622B2 - Glass for liquid crystal display substrates - Google Patents

Description

The present invention relates to a glass for a liquid crystal display substrate, and more particularly to a general-purpose liquid crystal display of an active matrix drive system using a field effect transistor of a polysilicon TFT (thin film transistor) type. The present invention relates to a glass for a liquid crystal display substrate suitable as a glass for a substrate to be used.

[Prior art] The liquid crystal display is a CRT (cathode ray tube,
It has advantages such as low power consumption, low voltage driving, and easy weight reduction and thickness reduction as compared with a cathode ray tube (CRT). Above all, an active matrix driving type liquid crystal display using a TFT (thin film transistor) type field effect transistor can easily provide a large number of scanning electrodes, so that it is easy to increase the density and definition of pixels. Because of its high duty ratio and capable of transmissive display, it has attracted attention as a full-color display replacing CRT.

An active matrix drive type liquid crystal display using a TFT type field effect transistor is composed of an amorphous silicon (α-Si) TFT type or a polysilicon (P), depending on the material of a semiconductor transistor formed on a transparent substrate such as glass or quartz. -Si) It can be divided into TFT type and so on.
Since the P-Si type is easier to achieve higher pixel density and higher definition than the α-Si type, and can incorporate drive circuits on the same substrate, the focus of R & D is gradually increasing. P
-Moving to Si type.

Both α-SiTFT and P-SiTFT are formed by forming an α-Si film or a P-Si film on a transparent substrate and then repeatedly performing a patterning step based on photolithography. For this reason, the transparent substrate on which the TFT is formed is required not only to have a linear expansion coefficient close to the linear expansion coefficient of the TFT material, but also to have excellent heat resistance, excellent chemical durability, and the like. You.

As a transparent substrate that satisfies such requirements, there is silica glass, but because of its high cost, it is not suitable as a general-purpose liquid crystal display substrate. For this reason, barium borosilicate alkali-free glass is frequently used as a substitute for silica glass in α-Si TFT type general-purpose liquid crystal displays.

[Problems to be Solved by the Invention] However, barium borosilicate alkali-free glass is
-When used as a substrate of a SiTFT type liquid crystal display, P-SiTFT is formed at a higher temperature than α-SiTFT, and thus has a problem in terms of heat resistance.

Accordingly, an object of the present invention is to provide a strain point which has a linear expansion coefficient close to that of P-Si and can be used as a substrate of a P-SiTFT type liquid crystal display, and which is frequently used in the process of forming P-SiTFT. Has good resistance to hydrofluoric and nitric acids, practical melting properties, and practical moldability.
An object of the present invention is to provide a glass for a liquid crystal display substrate, which is suitable as a substrate for a SiTFT type general-purpose liquid crystal display.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and the glass for a liquid crystal display substrate of the present invention comprises SiO ₂ ,
Contains B ₂ O ₃ , Al ₂ O ₃ , MgO, CaO, SrO, and BaO in a total amount of 95 mol% or more, and the content of each component in terms of mol% is SiO ₂ 62% to 68% B ₂ O ₃ 8% or more and less than 12% Al ₂ O ₃ 9% or more and 13% or less MgO 1% or more and 5% or less CaO 3% or more and 7% or less SrO 1% or more and less than 3% BaO 1% or more and less than 3% SrO + BaO 2% or more 5 % Or less.

 Hereinafter, the present invention will be described in detail.

The glass for a liquid crystal display substrate of the present invention is, as described above, SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , MgO, CaO, SrO, and BaO
Is contained in a total amount of 95 mol% or more, and the content of each component is limited to the above value in terms of mol%. The reasons for these limitations are as follows.

If the content of SiO ₂ exceeds 68 mol%, the viscosity becomes high and the meltability decreases, and if it is less than 62 mol%, the strain point of the obtained glass is too low.

When the content of B ₂ O ₃ is 12 mol% or more, the strain point of the obtained glass is too low, and the nitric acid resistance is lowered. When the content is less than 8 mol%, the viscosity is increased and the melting property is lowered, The hydrofluoric acid resistance of the obtained glass decreases.

When the content of Al ₂ O ₃ exceeds 13 mol%, the devitrification resistance of the obtained glass is reduced, and when the glass is brought into contact with hydrofluoric acid, the glass surface is easily clouded by hydrofluoric acid. On the other hand, when the content of Al ₂ O ₃ is less than 9 mol%, the strain point of the obtained glass is too low.

MgO is the most effective component in alkaline earth oxides as a component for lowering the expansion coefficient and viscosity of the obtained glass, so it must be contained in an amount of 1 mol% or more.
If the content exceeds 5 mol%, the devitrification resistance of the obtained glass decreases.

In addition, CaO has almost the same action as MgO, so it needs to be 3 mol% or more. However, if it exceeds 7 mol%, the devitrification resistance of the obtained glass decreases.

Since both SrO and BaO are effective components for improving the devitrification resistance of the obtained glass, they are required to be 1 mol% or more, respectively. Are also components that lower the strain point and increase the expansion coefficient, so their contents are each limited to less than 3 mol%, and the total amount of both is also limited to 5 mol% or less.

And, as described above, the total amount of these components is 95
It is limited to mol% or more. Even if the content of each component is within the above range, if the total amount of these components is less than 95 mol%, desired characteristics cannot be obtained, which is not preferable.

By defining the components of glass and their contents, and the total amount of each component as described above, the P-Si TFT type liquid crystal display has a linear expansion coefficient close to the linear expansion coefficient of P-Si, and Glass having a strain point that can be used as a substrate, that is, an average linear expansion coefficient at 100 to 300 ° C. of 34 × 10 ^{−7 to} 39 × 10 ⁻⁷ deg ⁻⁷ cm ⁻¹ and a strain point of 630 ° C. or higher You can get some glass. This glass is also excellent in meltability and moldability.

Further, the glass for a liquid crystal display substrate of the present invention includes the aforementioned SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , MgO, CaO, SrO, and BaO
Other components (hereinafter referred to as subcomponents) in a total amount of 5 mol%
The following can be contained.

It is preferable that at least one selected from the group consisting of ZnO, PbO, La ₂ O ₃ , ZrO ₂ , As ₂ O ₃ , and Sb ₂ O ₃ is contained as an accessory component. And it, the content of each sub-component by mol% are ZnO 2% or less PbO 1% or less La ₂ O ₃ 1% or less ZrO ₂ 1% or less As ₂ O ₃ 2% or less Sb ₂ O ₃ 2% or less Is particularly preferred. In addition, the range of the content of each of these by-products includes 0%.

ZnO is effective as a component for lowering the viscosity without increasing the expansion coefficient of the obtained glass, and for improving the devitrification resistance, but is a component for lowering the strain point of the obtained glass and lowering the nitric acid resistance. Therefore, when it is contained, the content is particularly preferably 2 mol% or less.

PbO is effective as a component for improving the devitrification resistance of the obtained glass, but since it is also a component for lowering the strain point of the obtained glass and increasing the viscosity at the time of melting, when it is contained, 1 mol% or less is contained. Is particularly preferred.

La ₂ O ₃ is effective as a component for improving the devitrification resistance without lowering the strain point of the obtained glass, but is also a component that reduces the nitric acid resistance of the obtained glass while being expensive. When it is contained, the content is particularly preferably 1 mol% or less.

ZrO ₂ raises the strain point of the obtained glass and is effective as a component for improving hydrofluoric acid resistance and nitric acid resistance.However, since it is also a component for reducing the devitrification resistance of the obtained glass,
When it is contained, the content is particularly preferably 1 mol% or less.

As ₂ O ₃ and Sb ₂ O ₃ are each a necessary component as a defoaming agent. However, in order to damage a melting device such as a platinum crucible or a current-carrying device, when they are contained, 2 mol% or less is particularly preferable. .

The glass for a liquid crystal display substrate of the present invention uses, as a raw material of each component, an oxide, a carbonate, a nitrate, a hydroxide, and the like which are generally used as a raw material of the glass. It is obtained by weighing and mixing so that the mixture is melted at 1500 to 1600 ° C. using a usual glass melting apparatus, defoaming and homogenizing, then forming into a predetermined shape, and gradually cooling.

EXAMPLES Examples of the present invention will be described below.

Example 1 Silica powder, boric acid, alumina, magnesium carbonate, calcium carbonate, strontium nitrate, barium carbonate and arsenous acid were used as raw materials, and these were converted to oxides in Table-1.
After being weighed and mixed so as to have the composition shown in the following, the present invention is melted at 1600 ° C., defoamed, homogenized, formed into a plate shape, and gradually cooled to give a plate shape of 120 × 150 × 50 mm. Was obtained for a liquid crystal display substrate.

Table 1 shows the average linear expansion coefficient at 100 to 300 ° C (hereinafter referred to as α _{100 to 300} ), the strain point, and the viscosity at 1500 ° C of the obtained glass.

The hydrofluoric acid resistance and nitric acid resistance of the obtained glass were evaluated in the following manner.

-Hydrofluoric acid resistance A sample obtained by polishing the obtained glass is immersed in a 5% HF aqueous solution at 25 ° C for 3 hours, and after drying, the weight loss of the sample is converted into an amount per unit area and per unit time. The hydrofluoric acid resistance was evaluated.

・ Nitric acid resistance A sample obtained in the same manner as in the case of
After immersion in a 30% HNO ₃ aqueous solution for 3 hours and drying, the weight loss of the sample was converted into an amount per unit area and per unit time, and the nitric acid resistance was evaluated.

 These conversion values are also shown in Table 1.

Further, about 100 g of the obtained glass is placed in a platinum crucible having a capacity of 100 cc, and the platinum crucible is covered with a platinum lid, and is heated at 1100 ° C. for 24 hours.
Crystals inside glass after standing for a while (devitrification)
The occurrence of occurrence was observed under a microscope, and the devitrification resistance was evaluated. Table 1 also shows the results of the microscopic observation.

Examples 2 to 5 Silica powder, boric acid, alumina, magnesium carbonate, calcium carbonate, strontium nitrate, barium carbonate, zinc white, lead nitrate, lanthanum oxide, zirconium oxide, arsenous acid and antimony oxide were used as raw materials, and these were converted to oxides. After weighing and mixing so as to have the composition shown in Table 1, the mixture was melted at 1500 to 1600 ° C., defoamed, homogenized, formed into a plate, gradually cooled, and the same as in Example 1. Shaped glass for liquid crystal display substrates was obtained.

Α _{100-300 of} each glass obtained, strain point, and 1500 ° C
Is shown in Table 1.

Further, the hydrofluoric acid resistance and the nitric acid resistance of each of the obtained glasses were evaluated in the same manner as in Example 1. Table 1 also shows the converted values at this time.

Further, the devitrification resistance of each of the obtained glasses was evaluated in the same manner as in Example 1. The results of each microscope observation at this time are also shown in the table.
It is shown in FIG.

Comparative Example 1 As shown in Table 1, a glass having a composition similar to barium borosilicate non-alkali glass, which has been conventionally used as a substrate of an α-Si TFT type liquid crystal display, was obtained.

Table 1 shows α _{100 to 300} , the strain point, and the viscosity at 1500 ° C. of the obtained glass.

The hydrofluoric acid resistance and nitric acid resistance of the obtained glass were evaluated in the same manner as in Example 1. Table 1 also shows the converted values at this time.

Further, the devitrification resistance of the obtained glass was evaluated in the same manner as in Example 1. The results of microscopic observation at this time are also shown in Table 1.

As is clear from Table 1, α _{100 to 300} of the glass for a liquid crystal display substrate of the present invention obtained in Examples 1 to 5 is
36 × 10 ^{−7 to} 39 × 10 ⁻⁷ deg ⁻¹ · cm ⁻¹ , which is close to the linear expansion coefficient of P-Si. Further, each glass has a strain point of 630 ° C. or higher, and can be used as a substrate of a P-SiTFT type liquid crystal display.

In addition, the viscosity at 1500 ° C is 10 ³
It is less than poise, indicating that it has practical melting properties.

Furthermore, the weight loss when immersed in a 5% HF aqueous solution is 7 to
9 mg / cm ² · hr, weight loss when immersed in 30% HNO ₃ aqueous solution is 4 × 10 ^{-2 to} 12 × 10 ^-2 mg / cm ² · hr, respectively. It turns out that it is excellent. During both the treatment with the 5% HF aqueous solution and the treatment with the 30% HNO ₃ aqueous solution, the phenomenon that the glass surface became cloudy was not observed.

Further, in any of the glasses, generation of crystals was not observed after standing at 1100 ° C. for 24 hours. This shows that the devitrification temperature of each glass is 1100 ° C. or less, and that it has practical moldability.

On the other hand, the alkali-free barium borosilicate glass of Comparative Example 1 has no problem with hydrofluoric acid resistance, nitric acid resistance, melting property, and moldability. However, the glass for a liquid crystal display substrate of the present invention obtained in Examples 1 to 5 can be used. The strain point is low and α _100-300 is large.

[Effects of the Invention] As described above, the glass for a liquid crystal display substrate of the present invention has a linear expansion coefficient close to the linear expansion coefficient of P-Si, and is used as a substrate of a P-Si TFT type liquid crystal display. It has a usable strain point, good resistance to hydrofluoric acid and nitric acid frequently used in the molding process of P-Si TFT, practical melting property, and practical molding property.

Therefore, by implementing the present invention, P-SiTFT
It is possible to provide a glass for a liquid crystal display substrate, which is suitable as a substrate for a general-purpose liquid crystal display having a shape.

Claims (3)

(57) [Claims] (1) The composition contains 95 mol% or more of SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , MgO, CaO, SrO and BaO in total, and the content of each component in terms of mol% is SiO ₂ 62 % or more 68% or less B ₂ O ₃ 8% or more and 12% less than Al ₂ O ₃ 9% to 13% less MgO 1% or more than 5% CaO 3% or more and 7% or less SrO 1% or more less than 3% BaO 1% or more A glass for a liquid crystal display substrate, wherein SrO + BaO is less than 3% and 2% or more and 5% or less. 2. In addition to SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , MgO, CaO, SrO, and BaO, ZnO, PbO, La ₂ O ₃ , ZrO ₂ , As ₂ O ₃ , and S
b ₂ O at least one of claims, characterized in that they contain in total 5 mol% or less ₃ is selected from the group consisting of (1) a liquid crystal display glass substrate according. (3) ZnO, PbO, La ₂ O ₃ , ZrO ₂ , As ₂ O ₃ , and Sb
_At least one selected from the group consisting of ₂ O ₃ is contained in a total amount of 5 mol% or less, and the content of each component in terms of mol% is 2% or less of ZnO 1% or less of PbO 1% or less of La ₂ O ₃ ZrO ₂ less than 1% as ₂ O ₃ less than 2% Sb ₂ O ₃ claims, characterized in that 2% or less (2) a liquid crystal display glass substrate according.