TWI524115B - A glass substrate for a flat panel display and a method for manufacturing the same, and a liquid crystal display - Google Patents

Description

Glass substrate for flat panel display, method of manufacturing the same, and liquid crystal display

The present invention relates to a glass substrate for a flat panel display, a method of manufacturing the same, and a liquid crystal display.

For a glass substrate used for a flat panel display such as a liquid crystal display or a plasma display, there is a requirement for internal defects required to exist in the glass substrate. Dispose of the glass substrate that does not meet the standard, etc.

However, in the case where the internal defect is a bubble which does not block light, even if the glass substrate has an internal defect, it is not discriminated as a defective product. (Refer to Patent Document 1).

On the other hand, in the case of an internal defect that does not have translucency such as a foreign matter, a strict standard is applied, particularly in the case of a glass substrate for a liquid crystal display, in the case where an internal defect exceeding a specific size exists in the glass substrate. It is judged to be a defective product.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4618426

It is an object of the present invention to provide a glass substrate which can be used for a high contrast flat panel display, a method of manufacturing the same, and a liquid crystal display.

As a result of intensive research, the present inventors have found that, for example, in a high contrast liquid crystal display such as an IPS (In-Place-Switching) method or a VA (Virtical Alignment) method, the quality of the prior liquid crystal display. The convex portion of the main surface of the glass substrate which is not problematic affects the quality of the display to a large extent. At this time, it was found that even if the internal defect does not have translucency and the long side length of the internal defect exceeds 50 μm, as long as the short side length is less than 5 μm, the convex portion caused by the internal defect is not formed on the main surface of the glass substrate. Above a certain height, it can also be used for a glass substrate suitable for a high-quality display. More specifically, it has been found that even in the case where a convex portion is present on the glass substrate, when the height of the convex portion is less than 0.15 μm, the quality is not a problem even if the convex portion is used for the surface on the device formation side.

The inventors have completed the present invention based on the above findings.

That is, a glass substrate for a flat panel display according to an aspect of the present invention is characterized in that a glass substrate including a light-shielding internal defect having a long side length exceeding 50 μm and a short side length is used as a flat display glass substrate. It is less than 5 μm; and a convex portion formed at a position on the main surface of the glass substrate corresponding to the position of the internal defect, and the height from the main surface is less than 0.15 μm.

If the internal defects of the light-shielding property are present in the glass, there is a problem in display quality due to the defect of the display pixel or the like.

Further, when an internal defect exists in the vicinity of the main surface of the glass substrate, a convex portion is easily formed on the main surface of the glass substrate.

In particular, when a glass substrate having a convex portion formed on a main surface due to an internal defect exceeding a specific size is used for a high-contrast display, there is a problem in quality, and it is always judged to be a defective product. However, it is also known that even if a convex portion formed by an internal defect having a long side length of more than 50 μm and a short side length of less than 5 μm exists on the main surface of the glass substrate, the height of the convex portion from the main surface of the glass substrate Less than 0.15μm Even when used for high-contrast displays, there is no problem.

Therefore, in the present invention, a glass substrate which has been treated as a defective product only because of the internal defects described above is used as a product, and the yield of the glass substrate can be improved.

The inner defect may have a long side length of 200 μm or less, a short side length of 1 μm or more, a height of the convex portion from the main surface of less than 0.10 μm, and the internal defect may be less than 50 μm from the main surface. Depth area.

Even if the internal defect having an inner side length of 200 μm or less and a short side length of 1 μm to 10 μm has a long side length of more than 50 μm, it is difficult for the naked eye to confirm its existence. Therefore, a glass substrate having an internal defect of such a size is targeted here.

Further, the length of the long side of the internal defect may be more than 50 μm and less than 80 μm, and the length of the short side may be less than 1 μm.

The above internal defects may also be linear platinum. The production of a glass substrate may be carried out using a reaction apparatus made of platinum or a platinum alloy. For example, when an alkali-free glass or a glass containing a small amount of alkali is used as a raw material to produce a glass substrate, the alkali-free glass contains a trace amount of alkali. The high temperature viscosity of the glass is high, so the temperature of the molten glass must be kept particularly high in the clarification tank. The clarification tank contains platinum or a platinum alloy from the viewpoint of heat resistance. However, in a clarification tank which is heated to a high temperature and is in a high temperature state, platinum is liable to volatilize from the inner wall surface of the clarification tank which is in contact with the gas phase space. Further, one part of the volatilized platinum is solidified again on the inner wall surface of the gas phase space, and crystal grains of platinum or platinum alloy are easily formed on the inner wall surface. Therefore, in the molten glass, a part of the crystal grains is detached from the inner wall surface of the clarification tank into linear platinum and falls into the glass substrate. Here, in particular, a glass substrate having linear platinum as an internal defect is used as a product when the length of the short side of the internal defect is less than 5 μm and the convex portion of the main surface of the glass substrate is less than 0.15 μm. .

The above internal defects may also exist in a depth region of less than 50 μm from the main surface.

The closer the internal defect is to the main surface of the glass substrate, the greater the height of the convex portion of the main surface of the glass substrate from the main surface, and accordingly, the easier it is to affect the quality of the display. However, in the glass substrate of the present invention, even in such a case, it can be used as an article as long as the specific conditions described above are satisfied.

Further, the length of the long side of the internal defect may be more than 50 μm and less than 80 μm, and the length of the short side may be less than 1 μm.

A liquid crystal display according to an aspect of the present invention is characterized in that the above-mentioned glass substrate for a flat display is used; and a color filter or a TFT (Thin Film Transistor) is formed on one main surface of the glass substrate. The device has a liquid crystal layer formed on the main surface side.

The above liquid crystal display is preferably used in the case of having a contrast ratio of 2000:1 or more.

A method of manufacturing a glass substrate for a flat panel display according to another aspect of the present invention includes a glass substrate manufacturing step and a glass substrate inspection step of performing a glass substrate manufactured in the glass substrate manufacturing step. And in the glass substrate inspection step, the glass substrate having the internal defect and having the convex portion is judged to be defective, and the internal defect does not have translucency, the long side length exceeds 50 μm, and the short side length is less than 5 μm. The portion is formed at a position on the main surface of the glass substrate corresponding to the position of the internal defect, and the height from the main surface is 0.15 μm or more.

According to this method, it is possible to select a glass substrate which can be used for a high-contrast flat display even if it contains internal defects which are not translucent and exceed the size of a specific size. Thereby, the product yield is improved.

The above internal defects may also have a long side length of more than 50 μm and less than 80 μm, and have a short side length of less than 1 μm.

The above internal defects may also be linear platinum.

According to the present invention, it is possible to obtain a glass substrate which can be used for a high-contrast flat display even if it contains an internal defect which does not have a light transmissive property exceeding a specific size.

1‧‧‧Glass substrate (flat display glass substrate)

3‧‧‧Main surface of the glass substrate

7‧‧‧ convex

10‧‧‧ Internal defects

11‧‧‧ glass substrate

20‧‧‧Liquid layer

22‧‧‧ Backlight

100‧‧‧melting device

101‧‧‧ melting furnace

101d‧‧‧ bucket

102‧‧‧clarification tube

103‧‧‧Stirring tank

103a‧‧‧Agitator

104‧‧‧Glass supply tube

105‧‧‧Glass supply tube

106‧‧‧Glass supply tube

200‧‧‧Forming device

210‧‧‧Formed body

300‧‧‧cutting device

D‧‧‧Deep area of the internal surface of the glass substrate from the internal defect

H‧‧‧ Height of the convex part

Short side length of L1‧‧‧ internal defects

Long side length of L2‧‧‧ internal defects

MG‧‧‧ molten glass

SG‧‧ ‧ flat glass

Fig. 1 is a view showing a cross section in the thickness direction of the glass substrate of the embodiment.

Fig. 2 is a view showing a cross section of a liquid crystal display device of the embodiment having the glass substrate shown in Fig. 1;

Fig. 3 is a view showing an example of a flow of a method of manufacturing a glass substrate of the embodiment.

Fig. 4 is a view schematically showing an example of an apparatus for performing the melting step to the cutting step in the embodiment.

Hereinafter, a method for producing a glass substrate and a glass substrate of the present invention, and a liquid crystal display will be described.

(glass substrate)

Fig. 1 is a cross-sectional view in the thickness direction of a glass substrate 1 according to an embodiment of the present invention.

First, an outline of the glass substrate 1 will be described.

The thickness of the glass substrate 1 is 0.1 to 1.5 mm, and the upper limit of the thickness is preferably 1.1 mm, 0.7 mm, and 0.5 mm, and the optimum upper limit is 0.4 mm. On the other hand, the lower limit of the preferred thickness is 0.2 mm.

The size of the glass substrate 1 is 500 to 2500 mm × 2500 to 3500 mm (length in the short side direction × length in the longitudinal direction).

Examples of the glass substrate 1 include borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda lime glass, alkali silicate glass, alkali aluminosilicate glass, and alkali aluminosilicate glass. Wait. Furthermore, as a glass plate for liquid crystal display or organic EL (Electro- Luminescence, electroluminescent) is preferably a glass plate, preferably a glass plate which is substantially free of alkali or contains only a very small amount of alkali.

The glass substrate 1 is used for a flat panel display such as a liquid crystal display, a plasma display, or an organic EL display, and is preferably used for a high-contrast flat display. Examples of the high-contrast flat display include an IPS method or a VA liquid crystal display. Furthermore, the high contrast ratio means that the contrast ratio is about 2000:1 to 3000:1 or more.

In the present embodiment, the glass substrate 1 is used for a liquid crystal display, and one main surface 3 is a smooth surface for forming a thin film of a semiconductor element array or a color filter, and the other main surface is a smooth surface on which a polarizing filter is disposed. .

In Fig. 1, a glass substrate 1 for a liquid crystal display includes an internal defect 10 having no light transmissivity.

The internal defect 10 which does not have translucency is a defect of the light-shielding property which exists in the glass substrate 1. A part of the defect exposed to the main surface 3 of the glass substrate 1 is not included in the internal defect 10. In the present embodiment, the internal defect 10 is a linear platinum having a circular or triangular cross section. The linear platinum is considered to be an elongated and polygonal platinum foreign matter which is dropped into a molten glass and dropped into a molten glass by a device such as a clarification tank made of platinum or a platinum alloy. In the glass substrate, in the manufacturing step of the glass substrate, the molten glass flows in one direction, whereby the orientation of the plurality of linear platinum coincides with the above-described one direction. Specifically, the direction of the long side of the elongated linear platinum shown in Fig. 1 coincides with the flow direction (the direction of the arrow in Fig. 4) flowing through the flat glass of the forming apparatus 200 shown in Fig. 4 described below.

The length L2 of the long side of the internal defect 10 exceeds 50 μm, and the length L1 of the short side is less than 5 μm. Here, the length L2 of the long side is the length of the portion where the length of the inner defect 10 is the largest, and is usually the length of the extending direction of the glass substrate 1 (the horizontal direction of the paper in FIG. 1). Further, the length L1 of the short side is the length of the portion where the length is the largest in the direction substantially perpendicular to the direction of the length L2 of the long side, and is usually the length of the thickness direction of the glass substrate 1 (in the direction of the paper surface in FIG. 1). .

The glass substrate 1 in which the convex portion 7 (described below) is formed on the main surface 3 by the internal defect 10 having a long side length L2 of more than 50 μm is used for a liquid crystal display of a high contrast ratio of the IPS method or the VA method. When the quality of the display (visible display unevenness, pixel defects, etc.) may cause problems. However, even in the case where such an internal defect 10 exists, as long as the short side length L1 is less than 5 μm and the shape of the convex portion is less than 15 μm, even if the convex portion is caused by internal defects of light blocking property, it is used for high contrast. There is no problem with the quality of the display.

In the present embodiment, the internal defect 10 has, for example, a long side length L2 of 200 μm or less or 200 to 52 μm, and a short side length L1 of 1 μm or more or 1 to 4 μm. Further, the length of the long side of the convex portion 7 is substantially the same as or shorter than the length of the long side of the internal defect.

As another preferred aspect, regarding the shape of the internal defect 10, the long side length L2 of the internal defect 10 exceeds 50 μm and is less than 80 μm, and the short side length L1 is less than 1 μm. The short side length L1 is, for example, 0.1 μm or more. At this time, the protruding height of the autonomous surface of the convex portion 7 is less than 0.15 μm. Even in the presence of such internal defects 10 and convex portions 7, the quality of the display for high contrast is not at all problematic.

The height of the glass substrate 1 from the main surface 3 of the glass substrate 1 corresponding to the position of the internal defect 10 (hereinafter also referred to as the horizontal position of the internal defect 10) is not more than 0.15 μm from the main surface 3. For example, the convex portion 7 of 0.10 μm is not reached. Here, the height of the portion of the height h-shaped convex portion 7 which is the largest from the main surface 3 is the highest. The convex portion 7 formed at the position of the main surface 3 of the glass substrate 1 corresponding to the horizontal position of the internal defect 10 is considered to be formed by the internal defect 10. If the glass substrate 1 having such a convex portion 7 is used for a high-contrast liquid crystal display, it may affect the driving of the liquid crystal, but such a problem does not occur as long as the height h is less than 0.15 μm.

Here, the influence of the convex portion 7 on the driving of the liquid crystal will be described with reference to FIG. Fig. 2 shows a cross section in the thickness direction of the liquid crystal display of the embodiment manufactured using the glass substrate 1. The liquid crystal display is an IPS-type display. In FIG. 2, a layer of glass is laminated from above. The glass substrate 11, the liquid crystal layer 20, the glass substrate 1, and the backlight 22. The glass substrate 11 is a glass substrate containing the same glass material as the glass substrate 1, but does not have internal defects, and has no convex portion on the main surface. On the main surface of the glass substrate 11 on the liquid crystal layer 20 side, a TFT (Thin Film Transistor) and a pixel electrode (not shown) are arranged in a matrix. Liquid crystal is injected into the liquid crystal layer 20. The glass substrate 1 has an internal defect 10 as described above, and a convex portion 7 is formed on the main surface. The glass substrate 1 is disposed such that the main surface on the side where the convex portion 7 is formed faces the liquid crystal layer 20, and a color filter is formed on the main surface. Further, a polarizing filter (not shown) is disposed on each of the main surfaces of the glass substrates 11 and 1 opposite to the liquid crystal layer 20.

In the liquid crystal display, when the height of the convex portion of the glass substrate is, for example, about 0.2 μm, when a voltage is applied to the liquid crystal layer 20, the region of the glass substrate 1 in which the convex portion 7 is formed and the convex portion 7 are not formed. Compared to the surrounding area, the liquid crystal reacts at a low voltage and becomes brighter than the surrounding area in the display. On the other hand, when the voltage applied to the liquid crystal layer 20 is lowered, the area of the glass substrate 1 on which the convex portion 7 is formed is darker than the area around the display as compared with the area around the display. Thus, when there is a convex portion having a height of 0.15 μm or more on the main surface of the glass substrate, the liquid crystal is driven at a low voltage to generate a driving difference of the liquid crystal, whereby the contrast ratio is less than 1000:1. For example, in a liquid crystal display of about 500:1 to 800:1, a slight difference between the color development or the illuminating state of other regions (the surrounding area) is enhanced by the polarizing filter, and is regarded as being It is considered that the display is uneven. On the other hand, when the height h of the convex portion 7 is less than 0.15 μm, the driving difference of the liquid crystal as described above is not enhanced by the polarizing filter to such an extent that it can be regarded as uneven display. In the IPS liquid crystal display, liquid crystals are arranged horizontally (perpendicular to the light incident direction) on the glass substrate, and driven in the horizontal direction (in-plane direction) (the liquid crystal molecules are rotated in a plane parallel to the glass substrate) Control the amount of light transmitted. Therefore, in the case of the IPS method, if there is a convex portion 7 which protrudes to the surface of the glass substrate and has a height of 0.15 μm or more, the alignment of the liquid crystal and the driving angle are shifted, and the light transmission amount is changed to produce a panel. Local brightness is uneven. That is, in the IPS method, the influence of the convex portion 7 on the alignment of the liquid crystal is more Big.

In particular, since the convex portion 7 formed by the rod-like internal defect 10 such as linear platinum has a sharp rising angle (local bulge) with respect to the main surface 3 of the glass substrate 1, the gap between the liquid crystal layers 20 (plate) The region where the distance in the thick direction is narrowed (the region where the convex portion 7 is formed) is likely to be conspicuous. Further, since the convex portion 7 is formed by an internal defect having a long side length L2 whose long side length exceeds 50 μm, it is easy to be regarded as a convex region extending in the longitudinal direction. Since the height h of the convex portion 7 of the glass substrate 1 of the present invention is less than 0.15 μm, it can also be used for such a high-contrast display.

The inventors of the present invention considered that when a convex portion is formed on the main surface due to the presence of a light-shielding internal defect inside the glass substrate, since the state of the glass in the vicinity of the internal defect is different from that of the internal defect such as a bubble, The effect of the display display quality is more pronounced. One of the reasons why the internal defect of the light-shielding property affects the display quality of the display is that it is considered that the formation of the internal defect of the light-shielding property and the presence of the internal defect in the glass substrate have a slight influence on the state (for example, density) of the glass in the vicinity of the internal defect. The driving or convex shape of the liquid crystal is matched and the amount of light transmitted is also reduced, which significantly affects the display quality of the display.

The present invention is specific to a glass substrate of a liquid crystal display having high contrast even if such an internal defect affecting the quality is present.

In the glass substrate 1, even if the length of the long side of the internal defect 10 exceeds 50 μm and is 200 μm or less, the length of the short side is 1 μm or more and less than 5 μm, and the internal defect 10 exists at a depth of less than 50 μm from the main surface 3 of the glass substrate 1. In the region D, the internal defect 10 and the convex portion 7 may be provided as long as the height h of the convex portion 7 is 0.10 μm. The internal defect 10 exposed in the vicinity of the main surface makes it possible to bulge the main surface 3 of the glass substrate 1 to generate the convex portion 7. However, even if the internal defect 10 exists in the depth region D which is less than 50 μm from the main surface 3 of the glass substrate 1, when the height h of the convex portion 7 is less than 0.10 μm, the quality of the display for high contrast is qualitatively No problem.

The above glass substrate 1 includes the internal defect 10 which does not have translucency and has a long side length L2 exceeding a certain length, but the short side length L1 of the internal defect 10 is shorter than 5 μm, and the convex portion 7 formed on the main surface 3 is formed. Since the height h is lower than 0.15 μm, the quality of the display is not a problem even for a display with high contrast. Therefore, the glass substrate previously treated as a defective product can be utilized as a product, and the yield is improved.

Further, in another embodiment, the glass substrate 1 can also be used as a glass substrate (the above-described glass substrate 11) disposed on the TFT side in the liquid crystal display. In this case, even if the glass substrate is disposed such that the main surface on the side where the convex portion is formed faces the liquid crystal layer, it does not affect the quality of the display.

Further, the internal defect 10 may be plural in the glass substrate 1. The convex portion 7 may also have a plurality of main surfaces on the glass substrate.

(Method of manufacturing glass substrate)

Next, a method of manufacturing a glass substrate will be described.

Fig. 3 is a view showing an example of a flow of a method of manufacturing a glass substrate.

The method for producing a glass substrate of the present invention includes a glass substrate manufacturing step and an inspection step (step S8).

The glass substrate manufacturing step mainly includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a molding step (ST5), a slow cooling step (ST6), and a cutting step (ST7). ). In addition to this, a grinding step, a grinding step, a washing step, and the like are also included.

The melting step (ST1) is carried out in a melting furnace. In the melting furnace, molten glass is produced by putting the glass raw material into the liquid surface of the molten glass stored in the melting furnace and heating it. Further, the molten glass is flown from the outlet opening provided at the bottom of one inner side wall of the melting furnace to the downstream step.

Further, a clarifying agent is added to the glass raw material. From the viewpoint of lowering the environmental load, it is preferred to use tin oxide as a fining agent.

The clarification step (ST2) is carried out at least in the clarification tube. In the clarification step, by raising the temperature of the molten glass in the clarification tube, the bubble of O ₂ generated by the reduction reaction of the clarifying agent absorbs CO ₂ or SO ₂ contained in the molten glass, and the bubble floats to the molten glass. At the liquid level, the gas contained in the bubble is released into the gas phase space inside the clarification tube. Further, in the clarification step, the reducing substance obtained by the reduction reaction of the clarifying agent is subjected to an oxidation reaction by lowering the temperature of the molten glass. Thereby, the gas component such as O ₂ remaining in the bubbles of the molten glass is absorbed again in the molten glass, and the bubbles disappear. The oxidation reaction and the reduction reaction using the clarifying agent are carried out by controlling the temperature of the molten glass. Further, in order to release the gas released from the molten glass into the gas phase space to the atmosphere, the clarification pipe is provided with a vent pipe that communicates with the atmosphere.

In the homogenization step (ST3), the molten glass in the stirring tank supplied through the pipe extending from the clarification pipe is stirred by a stirrer to homogenize the glass component. Thereby, the composition unevenness of the glass which causes a stripe etc. can be reduced.

In the supply step (ST4), the molten glass is supplied to the forming apparatus through a pipe extending from the stirring tank.

The forming step (ST5) and the slow cooling step (ST6) are performed in the molding apparatus.

In the forming step (ST5), the molten glass is formed into a flat glass, and the flow of the flat glass is formed. The forming system uses an overflow down-draw method.

In the slow cooling step (ST6), the flat glass which flows after molding has a desired thickness and does not cause internal deformation, and further, is cooled without causing warpage.

In the cutting step (ST7), in the cutting device, the plate glass supplied from the forming device is cut into a specific length to obtain a plate-shaped glass plate. The cut glass sheet is further cut into a specific size to produce a glass substrate of a target size. Thereafter, the cross section of the glass substrate is ground and polished, and the glass substrate is cleaned.

Here, a glass sheet manufacturing apparatus that performs a melting step (ST1) to a cutting step (ST7) will be described with reference to Fig. 4 . Fig. 4 is a view schematically showing an example of a glass sheet manufacturing apparatus that performs the melting step (ST1) to the cutting step (ST7) in the present embodiment. The device mainly has melting The apparatus 100, the forming apparatus 200, and the cutting apparatus 300 are illustrated. The melting apparatus 100 includes a melting furnace 101, a clarification pipe (clarification tank body) 102, a stirring tank 103, and glass supply pipes 104, 105, and 106.

In the melting apparatus 100 shown in FIG. 4, the input of the glass raw material is performed using the bucket 101d. In the clarification pipe 102, the temperature of the molten glass MG is adjusted, and the clarification of the molten glass MG is performed by the oxidation-reduction reaction of a clarifier. Further, in the stirring tank 103, the molten glass MG is stirred by the agitator 103a to be homogenized. In the molding apparatus 200, the sheet glass SG is formed from the molten glass MG by using the overflow down-draw method of the formed body 210.

Further, a flow path forming member that forms a flow path from the melting furnace 101 shown in FIG. 4 to the molten glass MG of the molding apparatus 200, specifically, a glass supply pipe 104, a clarification pipe 102, a glass supply pipe 105, and a stirring tank 103 The flow path forming member that forms the flow path of the molten glass MG by the glass supply pipe 106 is made of platinum or a platinum alloy.

When the production (operation) of the glass substrate is started, such a flow path forming member made of platinum or a platinum alloy is heated in advance.

As the glass substrate produced by the melting device 100 and the molding device 200, the following glass composition glass is used. Therefore, the glass raw material is used in such a manner that the glass substrate has the following glass composition.

SiO ₂ 55~75 mol%, Al ₂ O ₃ 5~20 mol%, B ₂ O ₃ 0~15 mol%, RO: 5-20 mol% (R is Mg, Ca, Sr and Ba) All of the elements contained in the glass substrate, R' ₂ O: 0 to 0.8 mol% (R' is all the elements contained in the glass substrate in Li, K, and Na).

The above glass is an example of a glass having a high temperature and high viscosity. In such a glass, the molten glass is heated to a high temperature in order to defoam the viscosity of the appropriate molten glass in the clarification pipe 102. The temperature of the molten glass containing tin oxide as a clarifying agent and having a viscosity of 10 ^2.5 poise (1 poise = 0.1 Pa sec.) is, for example, 1500 to 1700 ° C, and heating is performed so that the temperature of the molten glass in the inside of the clarification tube 102 reaches 1600. Above °C. Therefore, volatile matter is volatilized from the inner wall of the clarification pipe 102 to cause agglomeration (precipitation) of the volatile matter.

Further, there is a case where the oxygen concentration in the gas phase space inside the clarification pipe 102 (the oxygen partial pressure in the gas phase space) is lowered by supplying an inert gas such as nitrogen gas to the gas phase space inside the clarification pipe 102. At least less than the concentration of oxygen in the atmosphere to reduce the amount of volatilization, and to reduce the temperature difference between the inner wall of the clarification pipe 102 (the wall surface exposed in the gas phase space) (for example, in the clarification pipe 102 connected to the gas phase space, The temperature difference is 150 ° C or less, thereby suppressing the precipitation of the volatilized platinum. However, in the long-term operation, the operating conditions are collapsed, and internal foreign matter due to volatilization and aggregation (precipitation) of platinum occurs. In this case, it is inevitable that the glass substrate has the above-described internal defects 10 and convex portions 7.

Returning to the description of the manufacturing method of the glass substrate, in the inspection step (ST8), after checking for the presence or absence of a defect, such as a bubble, the glass plate which inspected the favorable product is bundled as a final product. Further, in the inspection step (ST8), in addition to the presence or absence of the defect, the size of the convex portion formed on the main surface of the glass sheet is not checked for the internal defects having no light transmissivity, and whether the glass sheet is defective. Discrimination.

Determining whether the particular defective glass sheet as follows in terms of lines is determined by the malfunction is: comprising a non-optically transparent, the longitudinal length of more than 50 m, preferably more than 50μ _m and less than 80 m, short side length not An internal defect of up to 5 μm, preferably less than 1 μm, and a convex portion having a height of 0.15 μm or more from the main surface at a position of the main surface of the glass plate corresponding to the position of the internal defect in the direction in which the glass sheet extends . The presence of internal defects in the glass sheet is judged by an automatic inspection device or an inspector. For a glass plate which is judged to have an internal defect having no light transmissivity, for example, a long side length and a short side length of the internal defect, and the height and depth of the convex portion are measured using a laser microscope.

The method for producing a glass substrate has a packing step in addition to the above steps, and the bundle is In the package step, a plurality of laminated glass substrates are transferred to the ordering party.

When the length of the long side of the internal defect exceeds 50 μm, as described above, a convex portion is formed on the main surface of the glass substrate due to the internal defect, and the convex portion has a high possibility of affecting the quality of the display, but is internally When the length of the short side of the defect is less than 5 μm and the height of the convex portion of the main surface of the glass substrate is less than 0.15 μm, the operation of the liquid crystal is not affected, and no problem occurs. Even when used in a high-contrast display, it does not affect the quality of the display. Therefore, according to the above-described method for producing a glass substrate, in order to determine whether or not such a glass substrate is used as a product, it is possible to reduce whether or not the glass substrate is discarded, thereby improving the yield.

(Experimental example)

A sample having a linear platinum as a glass substrate having no translucent internal defects was screened out from the glass substrate produced by the overflow down-draw method. As a first example, a plurality of glass substrates were obtained: the linear platinum foreign matter size was The length of the long side is 52 to 200 μm, the length of the short side is 1 to 4 μm, and the main surface state due to the height of the convex portion of the linear platinum is 0.03 to 0.14 μm. Then, a plurality of liquid crystal displays of the same IPS type as those shown in FIG. 2 were produced. The sample of the glass substrate was disposed so that the convex portion faces the liquid crystal layer 20 side as a substrate on the color filter side. Further, on the TFT side, a separately formed glass substrate having no internal defects and convex portions was disposed (Example 1).

Further, in the same manner as in Example 1, a sample having a linear platinum as a glass substrate having no translucent internal defects was selected from the glass substrate produced by the overflow down-draw method, and as in Example 2, a plurality of glasses were obtained. Substrate: The linear platinum foreign matter has a length of 52 to 78 μm on the long side, a length of 0.1 μm on the short side to less than 0.98 μm, and a main surface state in which the height of the convex portion of the linear platinum is 0.03 to 0.14 μm. Further, a plurality of IPS liquid crystal displays were produced in the same manner as in the first embodiment. The sample of the glass substrate was disposed so that the convex portion faces the liquid crystal layer 20 side as a substrate on the color filter side. Further, on the TFT side, a separately formed glass substrate having no internal defects and convex portions was disposed (Example 2).

Further, a sample of a glass substrate having a height of 0.15 μm and 0.25 μm of the convex portion, a sample of a glass substrate having a short side length of 5 μm and 10 μm of the internal defect, and a sample of the glass substrate of Examples 1 and 2 were used. Liquid crystal display (Comparative Examples 1 to 4).

Further, a liquid crystal display (Comparative Example 5) was produced by using a sample of a glass substrate having a height of the convex portion of 0.15 μm to 0.2 μm, a short side length of the internal defect of 0.1 to 1 μm, and a long side length of 52 to 78 μm.

Further, in any of the glass substrates, linear platinum is present at a depth of less than 50 μm from the main surface. When the position of the linear platinum exists on the other surface side, there is a problem that the glass substrate is exposed to the surface when the glass substrate is formed. Therefore, in the case where the linear platinum is present in the glass substrate produced by the overflow down-draw method, it is preferably not present on the back side.

Furthermore, the above liquid crystal display is designed in such a manner that the frontal contrast reaches a ratio of 3000:1.

(Measurement of internal defects and convex parts)

The convex portion of the sample of the glass substrate is positioned in a horizontal direction in the main surface of the sample based on the defect data stored in the automatic inspection machine. Further, the long side length L2 and the short side length L1 of the internal defect, and the height h and the depth D of the convex portion were measured at a magnification of 2400 times using a laser microscope. The measurement results are shown in Table 1.

(Front view contrast)

In the dark room, the black display state of the liquid crystal display and the front view brightness in the white display state were measured using a brightness meter BM-5A (manufactured by TOPCON Co., Ltd.), and the front view contrast was calculated and confirmed.

(display uneven display)

Applying a voltage to the prepared liquid crystal display to drive the liquid crystal, from the front and the oblique direction of the liquid crystal display, visually observing a position away from the liquid crystal display by a certain distance, thereby displaying the confession display to the black display, and the black display to the white display Unrecognized display The condition was evaluated as A (available), and the case where the display was uneven was evaluated as B (defective product). The display unevenness is determined by comparison with a Boundary Sample. The results are shown in Table 1.

According to Table 1, when the height of the convex portion is less than 0.15 μm, the length of the short side of the internal defect is 1 to 4 μm, and the length of the long side is 52 to 200 μm (Example 1), unevenness in display is not confirmed, even if it is used for The high-contrast liquid crystal display has no problem in quality. Further, when the height of the convex portion is less than 0.15 μm, the length of the short side of the internal defect is less than 1 μm (0.98 μm or less), and the length of the long side is 52 to 78 μm (Example 2), no display unevenness is observed, that is, Used in high-contrast LCD monitors, there is no problem in quality. On the other hand, when the height of the convex portion was 0.15 μm or more (Comparative Examples 1 and 2), display unevenness was confirmed. Further, when the length of the short side of the internal defect was less than 5 μm (Example 1), display unevenness was not confirmed, and even for a liquid crystal display having high contrast, there was no problem in quality. On the other hand, when the short side length of the internal defect was 5 μm or more (Comparative Examples 3 and 4), display unevenness was confirmed.

The glass substrate for a flat panel display, the method for producing the glass substrate, and the liquid crystal display of the present invention have been described in detail above. However, the present invention is not limited to the above embodiment, and it goes without departing from the gist of the present invention. Make various improvements or changes.

1‧‧‧ glass substrate

3‧‧‧Main surface of the glass substrate

7‧‧‧ convex

10‧‧‧ Internal defects

D‧‧‧Deep defect from the depth of the main surface of the glass substrate

H‧‧‧ Height of the convex part

Short side length of L1‧‧‧ internal defects

Long side length of L2‧‧‧ internal defects

Claims (9)

A glass substrate for a flat panel display, characterized in that a glass substrate is used as a flat display glass substrate, the glass substrate comprising: an internal defect, which has no light transmissivity, a long side length of more than 50 μm and a thickness of 200 μm or less, and a short side length a position of less than 5 μm; and a convex portion formed on a main surface of the glass substrate corresponding to the position of the internal defect, the height from the main surface is less than 0.15 μm; the thickness of the glass substrate is 0.1 to 1.5 mm And contains SiO ₂ 55-75 mol%, Al ₂ O ₃ 5-20 mol%, B ₂ O ₃ 0-15 mol%, RO 5-20 mol% (R represents Mg, Ca, Sr and All of the elements included in the glass substrate in Ba), R' ₂ O 0 to 0.8 mol% (R' represents all the elements contained in the glass substrate of Li, K, and Na). The glass substrate for a flat panel display according to claim 1, wherein the short side length of the internal defect is 1 μm or more, the height of the convex portion from the main surface is less than 0.10 μm, and the internal defect is less than 50 μm from the main surface. The depth area. The glass substrate for a flat panel display according to claim 1, wherein the length of the long side of the internal defect exceeds 50 μm and is less than 80 μm, and the length of the short side is less than 1 μm. The glass substrate for a flat panel display according to any one of claims 1 to 3, wherein the internal defect is linear platinum. A liquid crystal display device using the above-mentioned glass substrate for a flat panel display according to any one of claims 1 to 4, wherein a color filter or a TFT device is formed on one main surface of the glass substrate, A liquid crystal layer is provided on the main surface side. A liquid crystal display according to claim 5, which has a contrast ratio of 2000:1 or more. A method for manufacturing a glass substrate for a flat panel display, comprising: a glass substrate manufacturing step, which has a thickness of 0.1 to 1.5 mm, and contains SiO ₂ 55 to 75 mol %, Al ₂ O ₃ 5 to 20 mol %, B ₂ O ₃ 0~15 mol%, RO 5-20 mol% (R represents all elements contained in the above glass substrate in Mg, Ca, Sr and Ba), R' ₂ O 0 to 0.8 mol% ( R' denotes a glass substrate including all the elements in the glass substrate of Li, K and Na; and a glass substrate inspection step for inspecting the glass substrate produced in the glass substrate manufacturing step; and on the glass substrate In the inspection step, the glass substrate having the internal defect described later and having a convex portion to be described later is judged to be defective, and the internal defect does not have translucency, and the long side length exceeds 50 μm and is 200 μm or less, and the short side length is less than 5 μm. The position on the main surface of the glass substrate corresponding to the position of the internal defect is set to be 0.15 μm or more from the main surface. The method of producing a glass substrate for a flat panel display according to claim 7, wherein the internal defect has a long side length of more than 50 μm and less than 80 μm, and has a short side length of less than 1 μm. The method for producing a glass substrate for a flat panel display according to claim 7 or 8, wherein the internal defect is linear platinum.