JP2000169180A - Float glass for display substrate - Google Patents

Abstract

(57) [Summary] [0005] Deterioration of liquid crystal characteristics such as defects such as disconnection of electrode lines formed on the surface, insufficient capacity of pixel liquid crystal, and reduced adhesion of oxide layer is unlikely to occur, and the strain point is 580 ° C. The above-mentioned float glass for a display substrate is obtained. The present invention relates to a float glass having a strain point of 580 ° C. or more, wherein the content of Cl with respect to a base glass is from 0.01 to 0.01.
0.09% by weight of float glass for display substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a float glass used for a display substrate such as a liquid crystal display substrate and a plasma display substrate.

[0002]

2. Description of the Related Art As a glass for a liquid crystal display (hereinafter referred to as LCD) substrate, a glass which does not contain alkali or has a small amount of alkali even if containing alkali, and has a high strain point and a small thermal expansion coefficient is required. Conventionally, aluminosilicate glass has been used as an alkali-free or low-alkali glass satisfying the above characteristics. The viscosity of such a glass in a molten state is higher than that of soda-lime silica glass widely used for window glass, for example, and it is difficult to remove bubbles, that is, to clarify. As a fining agent, arsenous acid, antimony oxide, a halogen element (F, Cl, Br, I), a sulfate, or the like is generally used.
Arsenous acid and antimony oxide are most effective.

[0003] On the other hand, most sheet glass represented by window glass is manufactured by a float method which can obtain a sheet glass having high flatness and smoothness at low cost. In the float method, molten glass is poured onto molten tin having a higher specific gravity than glass, and is formed while being spread on the molten tin in a plate shape. The float bath containing molten tin is kept in a reducing atmosphere to prevent oxidation of the molten tin.
Therefore, if a component that is easily reduced, such as arsenous acid or antimony oxide, is present in the glass, there is a possibility that metal deposition and accompanying coloring may occur.

[0004] Therefore, the fining agents that can be used for float-molded glass are limited, and it is generally difficult to use arsenous acid or antimony oxide. On the other hand, the above-mentioned problems do not occur with sulfates and halogen elements.

[0005] In view of the above, the LC to be float-molded
In alkali-free or low-alkali aluminosilicate glasses for D substrates (hereinafter referred to as float glass for LCD substrates), halogen elements and / or sulfates are often used as fining agents. All of the halogen elements F, Cl, Br, and I show the effect as a fining agent, but Cl is easily available as a raw material, has less volatilization than other halogen elements, and has a large effect as a fining agent. Used. As the sulfate, an alkali metal sulfate or an alkaline earth metal sulfate is usually used.

The steps of manufacturing a TFT-LCD using the float glass for an LCD substrate manufactured as described above are as follows. That is, the float glass is cut into a predetermined size to form a glass substrate. After washing the glass substrate, the glass substrate is put into a TFT-LCD manufacturing process. A gate electrode line (hereinafter simply referred to as an electrode line) and an oxide layer for gate insulation (hereinafter simply referred to as an oxide layer) are formed on one surface of a glass substrate, and a pixel electrode and the like are formed on the surface of the oxide layer. To form an array substrate. An RGB color filter and a counter electrode are formed on one surface of another glass substrate to form a color filter substrate. Next, a liquid crystal material is sandwiched and sealed between the array substrate and the color filter substrate to manufacture a TFT-LCD. In addition, general TFT
-On the LCD substrate, the line width of the electrode line is 5 to 10 μm
And the electrode line interval corresponding to the pixel pitch is 100 to 20
The cell gap of the liquid crystal is about 5 μm.

Conventionally, irrespective of the cleanliness of the above-mentioned washing process and TFT-LCD manufacturing process, defects such as disconnection of electrode lines, deterioration of liquid crystal characteristics such as insufficient capacity of pixel liquid crystal, deterioration of adhesion of oxide layer, etc. In some cases, these have been the causes of lower LCD manufacturing yields.

[0008]

SUMMARY OF THE INVENTION The present invention has a distortion point of 58.
An object of the present invention is to provide a float glass having a temperature of 0 ° C. or higher and which is unlikely to cause the above-described poor quality.

[0009]

According to the present invention, a distortion point is 580.
The present invention provides a float glass for a display substrate, wherein the float glass has a Cl content of 0.01 to 0.09% by weight based on the mother glass.

[0010] The present inventor: 1) When manufacturing a TFT-LCD using a float glass, defects such as disconnection of an electrode line and a pixel, which are generated regardless of the cleanliness of a cleaning process or a TFT-LCD manufacturing process. The causes of poor quality such as a decrease in liquid crystal characteristics such as insufficient capacity of the liquid crystal, a decrease in adhesion of the oxide layer, and the like are caused by deposits or dents present on the surface of the float glass. 2) The surface of the float glass not in contact with the molten tin That is, the generation of deposits present on the top surface, or the formation of depressions on the surface of the float glass, and the C of the float glass
It has been found that there is a correlation between the 1 content and the SO ₃ content, and the present invention has been achieved. Here, the deposit is mainly composed of metallic tin or a tin compound.

That is, Cl or Cl and SO
It has been found that the mechanism for depositing metallic tin or a tin compound on the top surface when the aluminosilicate glass containing ₃ is formed by the float method is as follows. Here, SO ₃ is supplied from sulfate or the like used as a fining agent.

Cl or SO ₃ contained in glass
Is eluted from the surface where the glass is in contact with the molten tin, that is, the bottom surface, and becomes tin chloride or tin sulfide. Tin chloride or tin sulfide exists in a gaseous state at a normal float bath temperature and atmosphere, has a high vapor pressure, and immediately escapes from molten tin to vaporize. The vaporized tin chloride or tin sulfide diffuses into the float bath atmosphere and is promptly reduced by hydrogen in the atmosphere to form metal tin particles. When the particles grow and grow and fall on the top surface of the ribbon-shaped glass (glass ribbon) in the float bath, they become metal tin deposits. Further, the tin compound deposit is oxidized after the metal tin deposit has left the float bath.

[0013] The depression present on the top surface is a shell of the metal tin deposit. That is, immediately after the glass ribbon exits the float bath, the metallic tin deposit is blown off from the top surface by the airflow flowing just above the top surface. The depression on the bottom surface is
Although the formation mechanism is unknown, it has been found that the frequency of occurrence increases with the Cl content or SO ₃ content in the glass.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The float glass for a display substrate in the present invention is a sheet glass produced by a float method, and is a sheet glass before a surface treatment such as formation of an electrode wire or an oxide layer is performed on the surface thereof. And includes, for example, those that have been cleaned and / or polished before the surface treatment is performed.

The display substrate in the present invention is a plate glass cut to a predetermined size, that is, a substrate glass having an electrode wire or an oxide layer formed on the surface thereof.
For example, an LCD substrate, a plasma display panel (hereinafter, referred to as PDP) substrate, and the like.

The strain point of the float glass for a display substrate of the present invention is 580 ° C. or higher. LC below 580 ° C
In the heat treatment process for manufacturing D, PDP, etc., there is a possibility that a problem of thermal deformation or a dimensional change of an LCD substrate, a PDP substrate, etc. may occur. In the following, a case used for manufacturing a TFT-LCD will be described.

The deposits present on the surface of the float glass referred to in the present invention mainly consist essentially of metallic tin or a tin compound. If the size is less than 20 μm, the thickness of the attached matter is negligible, the disconnection of the electrode wire is rare, and the capacity of the pixel liquid crystal is insufficient. However, when an electrode line is formed on an attachment having a size of 20 μm or more, the electrode line is more likely to be disconnected. In addition, when a pixel area is formed on the attachment, a pixel liquid crystal is formed. In this case, there is a high possibility that the liquid crystal characteristics may be deteriorated due to insufficient capacity of the liquid crystal, and in any case, the LCD manufacturing yield may be reduced. Those having a size of 300 μm or more have a small adhesive force to glass and can be removed by a general washing step, and there is little possibility of causing a problem. In the following, among the deposits present on the float glass surface, the size is 20 to 300.
μm is referred to as a deposit defect.

The depth existing on the float glass surface is 1 μm.
Depressions of m or more (hereinafter referred to as depression defects) cause disconnection of the electrode wires formed on the surface of the glass substrate or decrease in adhesion of the oxide layer formed on the surface of the glass substrate to the glass substrate. Lower the retention.

The case where the present invention is used in the manufacture of a TFT-LCD has been described above, but the present invention is not limited to this. Float glass for an STN-LCD substrate, float glass for a PDP substrate, etc. Oxide layer,
The present invention is applied to a float glass on which a thin film layer is formed.

The Cl content of the float glass for a display substrate of the present invention is 0.01 to 0.0 with respect to the base glass.
9% by weight. If it exceeds 0.09% by weight, the frequency of occurrence of deposit defects and pit defects increases, and it becomes difficult to use the glass as a display substrate glass. If it is less than 0.01% by weight, the refining effect is small. It is preferably at least 0.02% by weight, more preferably at least 0.03% by weight.
Here, “with respect to the base glass” means that the content is expressed in an external number.

Although SO ₃ of the float glass for a display substrate of the present invention is not an essential component, it may be contained up to 200 ppm with respect to the base glass for clarification or the like. 200
If it exceeds ppm, the frequency of occurrence of the deposit defect and the dent defect increases, and it may be difficult to use the glass as a display substrate glass. Preferably 120 ppm
Or less, more preferably 90 ppm or less, particularly preferably less than 50 ppm. Further, it is preferable to contain 1 ppm or more.

The alkali oxide of the float glass for a display substrate of the present invention is not an essential component, but may be contained up to 2.0% by weight based on the mother glass. 2.0% by weight
If it is too large, it may be difficult to use it as a glass for a display substrate, particularly as a glass for an LCD substrate.

[0023]

EXAMPLES "Examples 1 and 2 (all examples), Examples 3 and 4"
(All comparative examples) "Mother glass (alumino
Silicate glass) having a composition of SiO_Two: 56.5, A
l_TwoO_Three: 11, B_TwoO_Three: 6, MgO: 2, CaO: 3,
BaO: 15, SrO: 6.5, thickness 0.7 mm
Of the four types of float glass for LCD substrates
Content of Cl in base glass measured by X-ray method (simple content)
Position: weight%) and the top surface is 6.0 m.^TwoDeposit defects per hit
And the total number of hollow defects (unit: pieces)
It is shown in FIG. This float glass is Na
_TwoO, K_TwoO at 0.05% by weight and 0.01% by weight, respectively
Contained and its strain point is 635 ° C. In addition,
The sum of the number of points and the number of hollow defects must not exceed 40.
Is preferred.

Regarding the deposit defect and the hollow defect,
By a so-called edge light inspection for inspecting the main surface of the glass plate irradiated with light from the side surface of the glass plate in a dark room, deposits having a size of 20 to 300 μm and dents were examined. The inspection was performed on 50 300 mm × 400 mm glass plates. The total area of the inspected glass plate surface is 6.
0 m ² . The depth of the dent present on the top surface was measured using a laser microscope, and a pit having a depth of 1 μm or more was regarded as a dent defect.

The SO ₃ content (unit: ppm) was measured by the method described below. Table 1 also shows the results.
Shown in First, as a pretreatment, a glass sample was decomposed with hydrofluoric acid and hydrochloric acid. At this time, hydrogen peroxide was added as an oxidizing agent in order to prevent some of the sulfur from being reduced or volatilized.

Next, a 4% aqueous solution of sodium hydroxide 0.5
An oxidation trap containing 5 ml of hydrogen peroxide, 5 ml of hydrogen peroxide and 5 ml of ion-exchanged water is prepared. The three-necked flask containing the pretreated sample and the oxidation trap are set in a measuring vessel, and after purging the inside of the measuring vessel with nitrogen, about 8 ml of a reducing agent is added to the three-necked flask. The reducing agent is hypophosphorous acid 5 ml,
20 ml of hydroiodic acid and 3.5 g of sodium iodide were weighed out and heated at 200 ° C. for 3 to 4 hours while bubbling with nitrogen.

The three-necked flask is heated to 180 to 200 ° C. in a sand bath while gently flowing nitrogen gas, and gently boiled. By this operation, all the sulfur in the sample is S ^2-
And released as H ₂ S gas. This H ₂ S gas is introduced into the oxidation trap together with the nitrogen stream, and is collected in the form of SO ₄ ²⁻ . The sulfur in the oxidation trap was analyzed by an ICP emission spectrometer (SPS400, manufactured by Seiko Instruments Inc.).
Quantification using 0) gave the SO ₃ content. Note that SO ₃
Although the content of Example 2 is smaller than that of Example 1, the total number of deposit defects and the number of hollow defects of Example 2 is larger than that of Example 1. Example 1
Probably because it is smaller.

[0028]

[Table 1]

Examples 5-6 (Each Example), Examples 7-8
(All Comparative Examples) The composition of the mother glass (aluminosilicate glass) expressed by weight% is SiO ₂ : 60, Al ₂ O
_{3: 17, B 2 O 3} : 7, MgO: 4, CaO: 5, Sr
O: 7, it is about four LCD substrate thick float glass 0.7mm a, Cl content in mother glass (unit: wt%) and SO ₃ content (unit: ppm)
Table 2 shows the total (unit: number) of the number of adherent defects and the number of hollow defects per 6.0 m ^{2 of} the top surface. This float glass is made of Na ₂ O, K ₂ O,
BaO is 0.05% by weight, 0.01% by weight, respectively.
0.2% by weight, and its strain point is 665 ° C.

The Cl content, the SO ₃ content, the number of deposit defects and dent defects present on the top surface, and the depth of the dents present on the top surface were measured in the same manner as in Examples 1-4.

[0031]

[Table 2]

[0032]

According to the present invention, there is provided a float glass having a strain point of 580 ° C. or more, a defect such as a disconnection of an electrode wire formed on the surface thereof, a decrease in liquid crystal characteristics such as a lack of capacity of a pixel liquid crystal, A float glass for a display substrate, in which the adhesiveness of the oxide layer is unlikely to be reduced and the like, is obtained, and the production yield of LCDs, PDPs and the like is improved.

Continued on the front page (72) Inventor Masako Kawamoto 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Asahi Glass Co., Ltd. (72) Inventor Ryoji Akiyama 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. 2H090 JB02 JD15 JD17 4G062 AA18 BB06 DA06 DB04 DC03 DD01 DE01 DF01 EA01 EB02 EC02 ED03 EE03 EF03 EG04 FA01 FA10 FB01 FC01 FD01 FE01 FF01 FG01 FH01 FJ01 FK01 FL01 H01 H01 H01 H01 H01 H01 H JJ01 JJ03 JJ06 JJ07 KK01 KK03 KK05 KK07 MM12 MM27 NN29 5C040 GA09 KA07 KB11 KB28 5C094 AA03 AA32 AA42 AA53 AA54 BA31 BA43 EB02 FB02 FB03 FB15 JA01 JA20

Claims (3)

[Claims] 1. A float glass having a strain point of 580 ° C. or higher, wherein the content of Cl with respect to the mother glass is 0.01 to 0.01.
0.09% by weight of float glass for display substrates. 2. The SO ₃ content in the mother glass is 200
The float glass for a display substrate according to claim 1, wherein the content is at most ppm. 3. The float glass for a display substrate according to claim 1, wherein the content of the alkali oxide with respect to the mother glass is 2.0% by weight or less.