WO2015159419A1

WO2015159419A1 - Flat panel display glass substrate, method for manufacturing same, and liquid crystal display

Info

Publication number: WO2015159419A1
Application number: PCT/JP2014/061006
Authority: WO
Inventors: 濱上　耕
Original assignee: ＡｖａｎＳｔｒａｔｅ株式会社
Priority date: 2014-04-18
Filing date: 2014-04-18
Publication date: 2015-10-22
Also published as: KR20150137046A; KR101744431B1; KR20150142668A; CN105209966A; CN105209966B; JP5769895B1; JPWO2015159419A1; KR101657429B1

Abstract

As a flat panel display glass substrate having a high contrast, the present invention uses a glass substrate that has: an internal defect, which does not have translucency, and which has a long-side length longer than 50 μm, and a short-side length shorter than 5 μm; and a protruding section, which is at a position on a main surface of the glass substrate, said position corresponding to the position of the internal defect, and which has a height shorter than 0.15 μm from the main surface.

Description

Glass substrate for flat panel display, manufacturing method thereof, and liquid crystal display

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

Glass substrates used in flat panel displays such as liquid crystal displays and plasma displays have standards required for internal defects existing in the glass substrates. Glass substrates that did not meet the standards were discarded.

However, when the internal defect is a bubble that does not block light, a determination method that does not determine that the glass substrate is defective even if the glass substrate has an internal defect has been proposed. (See Patent Document 1).
On the other hand, strict standards are still applied to internal defects that do not have translucency, such as foreign matter, and particularly in glass substrates for liquid crystal displays, the glass substrate has a size exceeding a predetermined size. When an internal defect exists, it is determined as a defective product.

Japanese Patent No. 4618426

An object of the present invention is to provide a glass substrate that can be used for a high-contrast flat panel display, a manufacturing method thereof, and a liquid crystal display.

As a result of diligent study, the present inventor, for example, in a high-contrast liquid crystal display such as an IPS (In-Place-Switching) method, a VA (Virtical Alignment) method, etc. It has been found that the protrusions on the main surface of the substrate greatly affect the quality of the display. At this time, even if the internal defect does not have translucency, and the long side length of the internal defect exceeds 50 μm, the short side length is less than 5 μm, and the convex portion due to the internal defect is The present inventors have found that the glass substrate can be used for a high-quality display if it is not formed at a predetermined height or more on the main surface of the glass substrate. More specifically, even when the convex portion exists on the glass substrate, if the convex portion has a height of less than 0.15 μm, the convex portion is used as the surface on the device forming side. Also found that there is no problem in quality.
The present inventor completed the present invention based on the above findings.

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

If a light-blocking internal defect exists in the glass, a display quality problem may occur due to a lack of display pixels.
Further, when the internal defect exists in the vicinity of the main surface of the glass substrate, convex portions are easily formed on the main surface of the glass substrate.
In particular, glass substrates with convex portions formed on the main surface due to light-blocking internal defects exceeding a predetermined size will cause problems in terms of quality when used in high-contrast displays. It was determined. However, even if a convex portion formed due to 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 glass of the convex portion It has also been found that when the height from the main surface of the substrate is less than 0.15 μm, no problem occurs even when used for a high-contrast display.
Therefore, in the present invention, it is possible to use a glass substrate that has been treated as a defective product just because there is an internal defect as described above, even though it does not cause quality problems as a product. Thus, the yield of glass substrate manufacturing is improved.

The internal defect has a long side length of 200 μm or less, a short side length of 1 μm or more,
The height of the convex part from the main surface is less than 0.10 μm;
The internal defect may exist in a depth region of less than 50 μm from the main surface.
The internal defect has a long side length of 200 μm or less, and an internal defect having a short side length of 1 μm to 10 μm may exist with the naked eye even if the long side length exceeds 50 μm. Confusing. Therefore, here, a glass substrate having an internal defect of such a size is targeted.
The long side length of the internal defect may be more than 50 μm and less than 80 μm, and the short side length may be less than 1 μm.

The internal defect may be linear platinum. The production of the glass substrate may be carried out using a platinum or platinum alloy reaction apparatus. For example, when producing a glass substrate using non-alkali glass or alkali-containing glass as a raw material, these non-alkali glass and alkali Since the glass containing a trace amount has high viscosity at high temperature, it is necessary to keep the temperature of the molten glass particularly high in the clarification tank. The clarification tank is made of platinum or a platinum alloy from the viewpoint of heat resistance, but in a clarification tank that is in a high temperature state to heat the molten glass to a high temperature, platinum is likely to volatilize from the inner wall surface in contact with the gas phase space of the clarification tank. . Furthermore, part of the volatilized platinum is likely to resolidify on the inner wall surface of the gas phase space and form platinum or platinum alloy crystal grains on the inner wall surface. For this reason, some of the crystal grains may be detached from the inner wall surface of the clarification tank in the molten glass to form linear platinum and fall into the glass substrate. Here, particularly for a glass substrate having linear platinum as an internal defect, when the short side length 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, It is used as a product.

The internal defect may exist in a depth region of less than 50 μm from the main surface.
The convex portion of the main surface of the glass substrate has a higher height from the main surface as the internal defect is closer to the main surface of the glass substrate, and accordingly, the display quality is more likely to be affected. However, the glass substrate of the present invention can be used as a product even in such a case as long as the predetermined condition is satisfied.
The long side length of the internal defect may be more than 50 μm and less than 80 μm, and the short side length may be less than 1 μm.

A liquid crystal display according to one embodiment of the present invention is provided.
A liquid crystal display using the glass substrate for flat panel display described above,
A color filter or a TFT device is formed on one main surface of the glass substrate, and a liquid crystal layer is formed on the main surface side.

The liquid crystal display is preferably used when it has a contrast ratio of 2000: 1 or more.

A method for producing a glass substrate for a flat panel display according to another embodiment of the present invention,
A glass substrate manufacturing process, and a glass substrate inspection process for inspecting the glass substrate manufactured in the glass substrate manufacturing process,
In the glass substrate inspecting step, the glass substrate does not have translucency, has an internal defect having a long side length of more than 50 μm and a short side length of less than 5 μm, and corresponds to the position of the internal defect. A glass substrate having a convex portion which is formed at a position on the main surface and has a height from the main surface of 0.15 μm or more is determined to be defective.
According to this method, a glass substrate that can be used for a high-contrast flat panel display can be selected even if it has an internal defect with a size exceeding a predetermined size that does not have translucency. This improves the product yield.

The internal defect may have a long side length of more than 50 μm and less than 80 μm, and a short side length of less than 1 μm.
The internal defect may be linear platinum.

According to the present invention, it is possible to obtain a glass substrate that can be used for a high-contrast flat panel display even if it has an internal defect exceeding a predetermined size that does not have translucency.

It is a figure which shows the thickness direction cross section of the glass substrate of this embodiment. It is a figure which shows the cross section of the liquid crystal display of this embodiment provided with the glass substrate shown in FIG. It is a figure which shows an example of the flow of the manufacturing method of the glass substrate of this embodiment. It is a figure which shows typically an example of the apparatus which performs the melting process-cutting process in this embodiment.

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

(Glass substrate)
FIG. 1 shows a sectional view in the thickness direction of a glass substrate 1 according to an embodiment of the present invention.
First, the 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 values of the preferable thickness are 1.1 mm, 0.7 mm, and 0.5 mm, and the most preferable upper limit value 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 lateral 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 aluminogermanate glass. In addition, as a glass plate for liquid crystal displays and a glass plate for organic EL (Electro-Luminescence), it is preferable to apply a glass plate that substantially does not contain alkali or contains a very small amount of alkali.

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

In this embodiment, the glass substrate 1 is used for a liquid crystal display. One main surface 3 is a smooth surface on which a thin film such as a semiconductor element array or a color filter is formed, and the other main surface is a polarizing filter. Is a smooth surface.

In FIG. 1, the glass substrate 1 used for a liquid crystal display has the internal defect 10 which does not have translucency.
The internal defect 10 having no translucency refers to a light-shielding defect present in the glass substrate 1. What the part has appeared on 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 linear platinum having a circular or triangular cross section. Linear platinum is a platinum foreign substance having a long and narrow polygonal cross section, which is considered to have fallen into molten glass from an apparatus such as a clarification tank made of platinum or a platinum alloy during the production of a glass substrate. In the glass substrate, during the glass substrate manufacturing process, the molten glass flows in one direction, so that the plurality of linear platinum are aligned in one direction. Specifically, the direction of the long side of the elongated linear platinum shown in FIG. 1 is aligned with the flow direction (arrow direction in FIG. 4) of the sheet glass flowing through the forming apparatus 200 shown in FIG.

The internal defect 10 has a long side length L2 of more than 50 μm and a short side length L1 of less than 5 μm. Here, the long side length L2 is the length of the portion having the maximum length in the internal defect 10, and is usually the length in the extending direction of the glass substrate 1 (the horizontal direction in FIG. 1). . Further, the short side length L1 is the length of the portion having the maximum length in the direction substantially orthogonal to the direction of the long side length L2, and is usually in the thickness direction of the glass substrate 1 (the paper surface in FIG. 1). Length in the vertical direction).
Due to the internal defect 10 having a long side length L2 exceeding 50 μm, the glass substrate 1 on which the convex portion 7 (described later) is formed on the main surface 3 is a high-contrast liquid crystal display of the IPS mode and the VA mode. May cause problems in display quality (visible display unevenness, missing pixels, etc.). However, even if such an internal defect 10 exists, if the short side length L1 is less than 5 μm and the shape of the convex portion is less than 15 μm, the convex portion is caused by the light-blocking internal defect. Even if it is used, a problem in quality does not occur even if it is used for a high-contrast 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 long side length of the convex portion 7 is substantially the same as or shorter than the long side length of the internal defect.
As another preferable aspect, regarding the shape of the internal defect 10, the long side length L2 of the internal defect 10 is more than 50 μm and 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. In this case, the protrusion height from the main surface of the convex part 7 is less than 0.15 micrometer. Even if such an internal defect 10 and convex portion 7 are present, there is no problem in quality even when used for a high-contrast display.

The glass substrate 1 has a height h from the main surface 3 of less than 0.15 μm at the position of 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). For example, the convex part 7 which is less than 0.10 μm is formed. Here, the height h is the height of the portion of the convex portion 7 where the height from the main surface 3 is maximum. The protrusion 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 due to the internal defect 10. The glass substrate 1 having such convex portions 7 may affect the driving of the liquid crystal when used in a high-contrast liquid crystal display, but if the height h is less than 0.15 μm, No problem arises.

Here, with reference to FIG. 2, the influence of the projection 7 on the driving of the liquid crystal will be described. In FIG. 2, the cross section of the plate | board thickness direction of the liquid crystal display of this embodiment manufactured using the glass substrate 1 is shown. This liquid crystal display is an IPS display, and a glass substrate 11, a liquid crystal layer 20, a glass substrate 1, and a backlight 22 are laminated from above in FIG. The glass substrate 11 is a glass substrate made of the same glass raw material as the glass substrate 1, but has no internal defect and does not have a convex portion on the main surface. On the main surface of the glass substrate 11 on the liquid crystal layer 20 side, TFTs (Thin Film Transistor) and pixel electrodes (not shown) are arranged in a matrix. Liquid crystal is injected into the liquid crystal layer 20. The glass substrate 1 has the internal defect 10 as mentioned above, and the convex part 7 is formed in the main surface. The glass substrate 1 is arranged with the main surface on the side where the convex portions 7 are formed facing the liquid crystal layer 20, and a color filter is formed on the main surface. A polarizing filter (not shown) is disposed on each main surface of the

glass substrates

11 and 1 opposite to the liquid crystal layer 20.

In this liquid crystal display, when the height of the convex portion of the glass substrate is, for example, about 0.2 μm, when voltage is applied to the liquid crystal layer 20, the convex portion 7 is formed in the region of the glass substrate 1 on which the convex portion 7 is formed. The liquid crystal reacts at a lower voltage than the surrounding area where no is formed, and brightens faster than the surrounding area on 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 projections 7 are formed becomes darker than the surrounding area of the display compared to the surrounding area. As described above, when a convex portion having a height of 0.15 μm or more exists on the main surface of the glass substrate, the liquid crystal is driven at a low voltage, and a driving difference of the liquid crystal is generated, so that the conventional contrast (contrast ratio is reduced). A slight difference in color development or emission mode from other regions (surrounding regions), which was not a problem in a liquid crystal display of less than 1000: 1 (for example, about 500: 1 to 800: 1), is emphasized by the polarizing filter, It will be visually recognized as display unevenness. 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 emphasized so as to be visually recognized as display unevenness by the polarizing filter. . In an IPS liquid crystal display, liquid crystals are arranged horizontally on a glass substrate (perpendicular to the light incident direction) and driven in the horizontal direction (in-plane direction) (liquid crystal molecules in a plane parallel to the glass substrate). Rotate) to control light transmission. For this reason, in the case of the IPS system, if there is a projection 7 having a height of 0.15 μm or more protruding in the plane of the glass substrate, the liquid crystal alignment / drive angle is shifted, and the amount of light transmission is changed. Display unevenness such as local brightness. In other words, in the IPS system, the projection 7 has a great influence on the alignment of the liquid crystal.

In particular, the protrusion 7 formed due to the rod-like internal defect 10 such as linear platinum has a steep rise angle (locally rises) with respect to the main surface 3 of the glass substrate 1, so that the liquid crystal In the region where the gap (distance in the plate thickness direction) of the layer 20 is narrow (the region where the convex portion 7 is formed), the contrast difference is easily noticeable. Moreover, the convex portion 7 is easily formed as a convex region extending in the long side direction by being formed due to an internal defect having a long side length L2 having a long side length exceeding 50 μm. The glass substrate 1 of the present invention can be used for such a high-contrast display because the height h of the convex portion 7 is less than 0.15 μm.
The inventor of the present application, when a convex portion is formed on the main surface due to the presence of light-blocking internal defects inside the glass substrate, the state of the glass near the internal defects is different from the case of internal defects such as bubbles. For this reason, it is considered that the influence on the display display quality appears more remarkably. One reason why light-blocking internal defects affect display quality is that the presence of light-blocking internal defects in the glass substrate has a small effect on the state of glass near the internal defects (for example, density). It is conceivable that this, when combined with the driving of the liquid crystal and the convex shape described above, and the reduction in the amount of light transmission, significantly affect the display quality of the display.
The present invention specifies a glass substrate that can be employed in a high-contrast liquid crystal display even if such internal defects affecting quality are present.

In the glass substrate 1, the long side length of the internal defect 10 is more than 50 μm and 200 μm or less, the short side length is 1 μm or more and less than 5 μm, and the internal defect 10 is less than 50 μm from the main surface 3 of the glass substrate 1. Even if it exists in the depth area | region D, if the height h of the convex part 7 is 0.10 micrometer, you may have the internal defect 10 and the convex part 7. FIG. The internal defect 10 that appears in the vicinity of the main surface has a high possibility that the main surface 3 of the glass substrate 1 is raised and the convex portion 7 is generated. However, even when the internal defect 10 exists in the depth region D less than 50 μm from the main surface 3 of the glass substrate 1, if the height h of the convex portion 7 is lower than 0.10 μm, a high-contrast display There is no problem in quality even if it is used.

The glass substrate 1 described above has an internal defect 10 having a long side length L2 exceeding a predetermined length that is not translucent, but the short side length L1 is shorter than 5 μm and is formed on the main surface 3. Since the height h of the projected portion 7 is lower than 0.15 μm, there is no problem in display quality even if it is used for a high contrast display. Therefore, a glass substrate that has been treated as a defective product can be used as a product, and the yield is improved.

In other embodiments, the glass substrate 1 may be used as a glass substrate (the glass substrate 11 described above) disposed on the TFT side in the liquid crystal display. In this case, even if the glass substrate is arranged with the main surface on the side where the convex portions are formed facing the liquid crystal layer, the display quality is not affected.
A plurality of internal defects 10 may exist in the glass substrate 1. There may be a plurality of convex portions 7 on the main surface of the glass substrate.

(Glass substrate manufacturing method)
Next, the manufacturing method of a glass substrate is demonstrated.
In FIG. 3, the figure explaining an example of the flow of the manufacturing method of a glass substrate is shown.
The manufacturing method of the glass substrate of this invention is equipped with a glass substrate manufacturing process and an inspection process (step S100).

The glass substrate manufacturing process includes a melting process (ST1), a clarification process (ST2), a homogenization process (ST3), a supply process (ST4), a molding process (ST5), a slow cooling process (ST6), Cutting step (ST7). In addition to this, there are a grinding process, a polishing process, a cleaning process, and the like.
The melting step (ST1) is performed in a melting furnace. In a melting furnace, a glass raw material is put into a liquid surface of molten glass stored in a melting furnace and heated to make molten glass. Furthermore, molten glass is flowed toward the downstream process from the outlet provided in one bottom part of the inner side wall of the melting furnace.
A clarifier is added to the glass raw material. From the viewpoint of reducing environmental burden, it is preferable to use tin oxide as a fining agent.

The clarification step (ST2) is performed at least in the clarification tube. In the clarification process, when the molten glass in the clarification tube is heated, CO ₂ or SO ₂ contained in the molten glass is absorbed by the O ₂ bubbles generated by the reductive reaction of the clarifier and grows. Bubbles rise to the liquid surface of the glass, and the gas contained in the bubbles is released into the gas phase space in the clarification tube. Furthermore, in the clarification step, the reducing substance obtained by the reduction reaction of the clarifier undergoes an oxidation reaction by lowering the temperature of the molten glass. Thereby, gas components such as O ₂ in the foam remaining in the molten glass are reabsorbed in the molten glass, and the foam disappears. The oxidation reaction and reduction reaction by the fining agent are performed by controlling the temperature of the molten glass. In addition, a clarification pipe | tube is provided with the vent pipe connected to air | atmosphere in order to discharge | release the gas discharge | released from the molten glass to the gaseous-phase space to air | atmosphere.

In the homogenization step (ST3), the glass components in the stirring vessel supplied through the pipe extending from the clarification tube are stirred using a stirrer to homogenize the glass components. Thereby, the composition unevenness of the glass which is a cause of striae or the like can be reduced.

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

In the molding apparatus, a molding step (ST5) and a slow cooling step (ST6) are performed.
In the forming step (ST5), the molten glass is formed into a sheet glass to make a flow of the sheet glass. For forming, an overflow downdraw method is used.
In the slow cooling step (ST6), the sheet glass that has been formed and flowed is cooled to a desired thickness, so that internal distortion does not occur and warpage does not occur.

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

Here, with reference to FIG. 4, the glass plate manufacturing apparatus which performs a melting process (ST1)-a cutting process (ST7) is demonstrated. FIG. 4 is a diagram schematically illustrating an example of a glass plate manufacturing apparatus that performs the melting step (ST1) to the cutting step (ST7) in the present embodiment. The apparatus mainly includes a melting apparatus 100, a molding apparatus 200, and a cutting apparatus 300. 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 glass raw material is charged using the bucket 101d. In the clarification tube 102, the temperature of the molten glass MG is adjusted, and the clarification of the molten glass MG is performed using the oxidation-reduction reaction of the clarifier. Further, in the stirring vessel 103, the molten glass MG is stirred and homogenized by the stirrer 103a. In the forming apparatus 200, the sheet glass SG is formed from the molten glass MG by the overflow down draw method using the formed body 210.

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

Such a flow path forming member made of platinum or a platinum alloy is preheated when the production (operation) of the glass substrate is started.

As a glass substrate produced with the melting apparatus 100 and the shaping | molding apparatus 200, the glass of the following glass compositions is used. Accordingly, the glass raw material is used so 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 to 20 mol% (R is all elements contained in the glass substrate among Mg, Ca, Sr and Ba),
R ′ ₂ O: 0 to 0.8 mol% (R ′ is all elements contained in the glass substrate among Li, K, and Na).
The glass is an example of a glass having a high temperature viscosity. In such a glass, the molten glass is heated to a high temperature in order to perform defoaming with an appropriate viscosity of the molten glass in the fining tube 102. The temperature of the molten glass containing tin oxide as a fining agent and having a viscosity of 10 ^2.5 poise (1 poise = 0.1 Pa · sec) is, for example, 1500 to 1700 ° C., and the temperature of the molten glass inside the fining tube 102 Is heated to 1600 ° C. or higher. For this reason, a large amount of volatile substances are volatilized from the inner wall of the clarification tube 102, and there is a possibility that aggregation (precipitation) of the volatile substances occurs.
By supplying an inert gas such as nitrogen to the gas phase space inside the clarification tube 102, the oxygen concentration in the gas phase space inside the clarification tube 102 (oxygen partial pressure in the gas phase space) is at least atmospheric. The amount of volatilization is reduced by reducing the oxygen concentration to less than the oxygen concentration in the tube, and the temperature difference in the inner wall surface (wall surface exposed to the gas phase space) of the clarification tube 102 is reduced (for example, clarification in which the gas phase space communicates) In the tube 102, the temperature difference is set to 150 ° C. or less) to suppress the deposition of the volatilized platinum. However, during long-term operation, the operation conditions collapse and the platinum volatilization / Internal foreign matter may be generated due to aggregation (precipitation). In this case, it is inevitable that the glass substrate has the internal defect 10 and the convex portion 7 described above.

Returning to the description of the method for manufacturing the glass substrate, in the inspection step (ST8), the presence or absence of defects such as bubbles is inspected, and then a glass plate that has passed the inspection is packed as a final product. In addition, in the inspection step (ST8), in addition to the presence or absence of defects, the internal defects that do not have translucency and the size of the projections formed on the main surface of the glass plate are inspected to determine whether or not the glass plate is defective. Is determined.
Specifically, the determination as to whether or not the product is defective is not translucent, and the long side length exceeds 50 μm, preferably exceeds 50 μm and is less than 80 μm, and the short side length is less than 5 μm. The height from the main surface is preferably 0.15 μm or more at the position of the main surface of the glass plate corresponding to the position of the internal defect in the direction in which the glass plate extends, preferably having an internal defect of less than 1 μm. This is done by discriminating a glass plate having a convex portion as defective. The presence of internal defects in the glass plate is determined by an automatic inspection device or an inspector. For a glass plate that is determined to have an internal defect that does not have translucency, the long side length and short side length of the internal defect and the height and depth of the convex portion are measured using, for example, a laser microscope. The
The glass substrate manufacturing method includes a packaging process in addition to the above processes, and the plurality of glass substrates stacked in the packaging process are transported to a supplier.

When the long side length of the internal defect exceeds 50 μm, as described above, a protrusion is formed on the main surface of the glass substrate due to this, and the protrusion is likely to affect the display quality. When the short side length of the internal defect is less than 5 μm and the height of the convex portion on the main surface of the glass substrate is less than 0.15 μm, no problem occurs without affecting the operation of the liquid crystal. Even when used for high-contrast displays, the display quality is not affected. Therefore, according to the above glass substrate manufacturing method, by determining whether or not such a glass substrate is a defective product, the number of discarded glass substrates can be reduced and the yield can be increased. Can be improved.

(Experimental example)
A sample of a glass substrate having linear platinum as an internal defect having no translucency is selected from a glass substrate manufactured by an overflow down draw method. As Example 1, the size of the linear platinum foreign matter has a long side length. A plurality of glass substrates having a main surface state of 52 to 200 μm, a short side length of 1 to 4 μm, and a convex part height due to linear platinum of 0.03 to 0.14 μm were obtained. A plurality of IPS liquid crystal displays having the same structure as that shown in FIG. The sample of the glass substrate was arranged with the convex portion facing the liquid crystal layer 20 side as the substrate on the color filter side. In addition, the glass substrate which does not have an internal defect and a convex part produced separately was distribute | arranged to the TFT side (Example 1).
Further, as in Example 1, a sample of a glass substrate having linear platinum as an internal defect that does not have translucency is selected from a glass substrate manufactured by an overflow down draw method. The main surface of the platinum foreign matter has a long side length of 52 to 78 μm, a short side length of 0.1 μm to less than 0.98 μm, and a convex height due to linear platinum of 0.03 to 0.14 μm. A plurality of glass substrates having a state were obtained. Further, in the same manner as in Example 1, a plurality of IPS liquid crystal displays were manufactured. The sample of the glass substrate was arranged with the convex portion facing the liquid crystal layer 20 side as the substrate on the color filter side. In addition, the glass substrate which does not have an internal defect and a convex part produced separately was distribute | arranged to the TFT side (Example 2).
Moreover, it replaced with the sample of the glass substrate of Example 1, 2, the sample of the glass substrate whose convex part height is 0.15 micrometer and 0.25 micrometer, and the glass whose short side length of an internal defect is 5 micrometers and 10 micrometers. A liquid crystal display was prepared using each sample of the substrate (Comparative Examples 1 to 4).
Further, a glass substrate sample in which the height of the convex portion is 0.15 μm to 0.2 μm, the short side length of the internal defect is 0.1 to 1 μm, and the long side length is 52 to 78 μm is used. Thus, a liquid crystal display was produced (Comparative Example 5).
In any glass substrate, linear platinum was 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 it appears on the surface during slimming of the glass substrate after the panel is formed. For this reason, in the glass substrate manufactured by the overflow down draw method, when linear platinum exists, it is preferable not to exist in the back surface side.
The liquid crystal display was designed so that the front contrast was a contrast ratio of 3000: 1.

(Measurement of internal defects and protrusions)
As for the convex part of the sample of the glass substrate, the horizontal position on the main surface of the sample is specified based on the defect data accumulated in the automatic inspection machine. Further, the long side length L2 and short side length L1 of the internal defect and the height h and depth D of the convex part were measured at a magnification of 2400 times using a laser microscope. The measurement results are shown in Table 1.

(Front contrast)
In a dark room, a luminance meter BM-5A (manufactured by Topcon Corporation) was used to measure the front luminance in the black display state and the white display state of the liquid crystal display, and the front contrast was calculated for confirmation.

(Display unevenness of display)
Drive the liquid crystal by applying voltage to the created liquid crystal display, and display from white display to black display and from black display to white display by visual observation at a predetermined distance from the liquid crystal display from the front and oblique directions of the liquid crystal display The case where no unevenness was confirmed was evaluated as A (usable), and the case where display unevenness was confirmed was evaluated as B (defective product). Display unevenness is determined by comparison with a limit 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 short side length of the internal defect is 1 to 4 μm, and the long side length is 52 to 200 μm (Example 1) No display unevenness was observed, and there was no problem in quality even when used for a high-contrast liquid crystal display. Further, when the height of the convex portion is less than 0.15 μm, the short side length of the internal defect is less than 1 μm (0.98 μ or less), and the long side length is 52 to 78 μm (Example 2) No display unevenness was observed, and there was no problem in quality even when used for a high-contrast liquid crystal display. On the other hand, display unevenness was confirmed when the height of the convex portion was 0.15 μm or more (Comparative Examples 1 and 2). Moreover, when the short side length of the internal defect was less than 5 μm (Example 1), display unevenness was not confirmed, and there was no problem in quality even when used for a high-contrast liquid crystal display. 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.

As described above, the flat panel display glass substrate, the glass substrate manufacturing method, and the liquid crystal display according to the present invention have been described in detail. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. Of course, improvements and changes may be made.

1 Glass substrate (flat display glass substrate)
3 Main surface 7 of glass substrate 7 Convex part 10 Internal defect h Height of convex part D Depth region L1 from main surface of glass substrate of internal defect Short side length L2 of internal defect Long side length of internal defect

Claims

A glass substrate,
An internal defect having no translucency, a long side length of more than 50 μm, and a short side length of less than 5 μm;
A glass substrate having a convex portion formed at a position on the main surface of the glass substrate corresponding to the position of the internal defect and having a height of less than 0.15 μm from the main surface, a flat panel display glass substrate A glass substrate for a flat panel display, characterized by being used as:
The internal defect has a long side length of 200 μm or less, a short side length of 1 μm or more,
The height of the convex part from the main surface is less than 0.10 μm;
The glass substrate for a flat panel display according to claim 1, wherein the internal defect exists in a depth region of less than 50 μm from the main surface.
The glass substrate for a flat panel display according to claim 1, wherein the internal defect has a long side length of more than 50 µm and less than 80 µm and a short side length of 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 using the flat panel display glass substrate according to any one of claims 1 to 4,
A liquid crystal display, wherein a color filter or a TFT device is formed on one main surface of the glass substrate, and a liquid crystal layer is provided on the main surface side.
The liquid crystal display according to claim 5, which has a contrast ratio of 2000: 1 or more.
A glass substrate manufacturing process for manufacturing a glass substrate, and a glass substrate inspection process for inspecting the glass substrate manufactured in the glass substrate manufacturing process.
In the glass substrate inspection step, the glass substrate inspection step does not have translucency, has an internal defect having a long side length of more than 50 μm and a short side length of less than 5 μm, and corresponds to the position of the internal defect. A glass substrate for a flat panel display, characterized in that a glass substrate having a convex portion formed at a position on the main surface of the glass substrate and having a height of 0.15 μm or more from the main surface is determined as defective. Production method.
The method for 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 a short side length of less than 1 µm.
The manufacturing method of the glass substrate for flat panel displays of Claim 7 or 8 whose said internal defect is linear platinum.