JP2001180957A - Glass substrate for display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass substrate for a display with a controlled deflection during conveyance and heat buckling by heat treatment. SOLUTION: A glass substrate for a display of a rectangular shape with a short edge of 300 mm or more and with a thickness of 0.3 to 0.6 mm comprises that a deviation stress in the substrate plane measured in a short- transverse direction is distributed in a compression direction and that the maximum value of a deviation compressive stress in a parallel direction with a edge around each edge is 0.3 MPa or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glass substrate for a display, and more particularly, to a liquid crystal display (TFT-type).
LCD, STN-LCD), plasma display (P
DP), plasma assisted liquid crystal display (PAL)
C), electroluminescent display (E
L), Field Emission Display (FE)
D) and the like, and relates to a glass substrate for a flat panel display (a flat display).

[0002]

2. Description of the Related Art In a flat panel display, usually 2
Two glass substrates are used, and a light emitting mechanism and a light transmission control mechanism are formed between these two glass substrates. The glass used as a glass substrate is typically a non-alkali borosilicate glass (for example, manufactured by Asahi Glass Co., Ltd. [trade name: AN6]) in a TFT liquid crystal display.
35, AN100, etc.), soda-lime glass (for example, [trade name: AS] manufactured by Asahi Glass Co., Ltd.) for STN liquid crystal displays, and high strain point glass (for example, trade name, manufactured by Asahi Glass Co., Ltd.) for plasma displays. : PD20
0]) etc. are used.

[0003] These glass substrates are manufactured by a method such as a float method, a fusion method, or a slit down draw method. The glass ribbon formed into a certain thickness by these manufacturing methods is cut into a surface shape having a predetermined dimension and supplied as a glass substrate. Some glass substrates are subjected to a slow cooling treatment (annealing treatment) after molding in order to control the heat shrinkage (compaction) to a predetermined value.

[0004] In manufacturing a flat panel display using the above glass substrate, cleaning,
Through various processes such as film formation, pattern formation, heat treatment, and inspection. The glass substrate is sequentially transported between the steps to manufacture a display.

[0005] The glass substrate is usually housed in a cassette and stored in a vertical or horizontal state. When it is horizontal, it is generally stored with two or three sides supported. In the manufacturing process, the glass substrate is put in and taken out of the cassette by an arm, and is transported by the arm in many steps. The arms often hold both sides and / or the bottom side of the substrate in point, line or surface contact.

[0006] Many manufacturing processes include heat treatment at several hundred degrees Celsius. In order to uniformly heat the entire surface of the glass substrate, a hot plate is generally used. Depending on the application, in addition to metal or ceramic surface heating plates, hot plates that have various shapes and functions, such as those that have a vacuum suction mechanism and those that are sandwiched from both sides, are used depending on the application Have been.

[0007]

When the glass substrate is stored or transported, the glass substrate bends depending on the supporting method. In recent years, due to demands for larger and lighter display panels, glass substrates having a large area and a small thickness have been used, and larger deflections have been more likely to occur than in the past. The occurrence of deflection causes vibration of the glass substrate and collision of the glass substrate with another object, and causes problems such as cracking of the glass substrate and damage of a pattern formed on the glass substrate.

As a measure against deflection of a glass substrate, a glass substrate manufacturer has been working to develop a glass having a uniform thickness, a low-density composition, and a glass having a high longitudinal modulus. Further, manufacturers of display manufacturing apparatuses perform optimization of pin support positions, adjustment of glass substrate transfer speed, and the like. However, no attempt has been made to further reduce the amount of deflection defined by the physical properties and shape of glass.

As a phenomenon similar to the problem of the deflection of the glass substrate, there is a problem of the warpage of the glass substrate. This is because when the glass substrate is heated with a hot plate or the like, the temperature of the central portion of the glass substrate becomes higher than the temperature of the peripheral portion, and the central portion of the glass substrate expands more. It is a phenomenon that emerges.

It is considered that the above-mentioned thermal warpage of the glass substrate occurs due to the following reasons. First, the surface of the glass substrate that is in contact with the hot plate (the lower surface in the case of horizontal placement) is heated, and a temperature difference occurs in the thickness direction between the contact surface (the lower surface) and the non-contact surface (the upper surface). As a result, the contact surface has a larger thermal expansion amount and is deformed into a downwardly convex shape. Once the above deformation occurs, only the central portion of the glass substrate comes into contact with the hot plate surface, and the temperature distribution in the glass substrate surface is high at the central portion and low at the peripheral portions.
Since the central portion expands more and the contact between the glass substrate and the hot plate is only at the central portion, the shape of the glass substrate is stabilized in a warped shape by heat.

[0011] The thermal warpage of the glass substrate includes the density of the glass,
In addition to the longitudinal modulus, values such as the coefficient of thermal expansion and the coefficient of thermal conductivity influence. These values are physical properties determined by the glass composition. The coefficient of thermal expansion and the coefficient of thermal conductivity of glass do not differ greatly between substrates used for the same application, and are almost constant.

With respect to the thermal warpage of the glass substrate, manufacturers of display manufacturing apparatuses perform homogenization of the temperature distribution of the hot plate, pre-heating of the glass substrate, mechanical pressing of the glass substrate to the hot plate, and the like. Such measures are taken. However, no attempt has been made to make the glass substrate itself less likely to be thermally warped.

When a glass substrate undergoes thermal warpage, it not only affects a target heat treatment step, but also causes a problem such as cracking due to mechanical pressing. In addition, the warpage in the subsequent transfer step is increased, and the probability of vibration and cracking of the substrate is increased.

As described above, the deflection and thermal warpage of the glass substrate cause problems such as cracks in the manufacturing process of the flat panel display. In recent years, flat panel displays have become larger and lighter, and glass substrates have tended to be correspondingly larger and thinner. Larger and thinner glass substrates,
For example, in the case of a substantially rectangular glass substrate having a length of 300 mm or more on both sides, deflection and thermal warpage become larger, which has been a problem that the handling of the glass substrate becomes difficult.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a substantially rectangular surface shape with a short side of 300 mm or more, and a plate thickness of 0.3 mm or more and 6 mm or more.
mm or less, due to the residual strain in the glass substrate, the deviation stress in the substrate plane measured in the thickness direction, distributed in the compression direction along the periphery of the substrate, near each side Maximum deviation compressive stress in the direction parallel to the side is 0.3MP
a glass substrate for a display which is not less than a.

In such a glass substrate in which stress in the compression direction is distributed along the periphery of the substrate, when deflection or thermal warpage occurs, stress is applied in a direction to cancel the deflection. Glass substrates, especially large,
It is desirable as a thin glass substrate.

The glass substrate of the present invention is substantially rectangular, and includes a glass substrate in which the corners of the peripheral portion are cut off (corner cut). In addition, "the maximum value of the deviation compressive stress in the direction parallel to the side near each side is 0.3MP.
The expression “not less than a” means that the maximum value of the deviation compressive stress in a direction parallel to the side near any one of the four sides of the glass substrate is 0.3 MPa or more.

Further, the present invention provides a display glass substrate having a strain point of 570 ° C. or higher and used for a plasma display panel. The heat treatment temperature of the glass substrate in the plasma display panel manufacturing process often reaches around 550 ° C., but if the strain point of the glass substrate is higher than the heat treatment temperature in the plasma display manufacturing process, the residual strain is hardly alleviated.

The present invention also provides a display glass substrate having a strain point of 650 ° C. or higher and used for a liquid crystal display panel. Although the heat treatment temperature of the glass substrate in the manufacturing process of the liquid crystal display often reaches around 630 ° C., if the strain point of the glass substrate is higher than the heat treatment temperature in the manufacturing process of the liquid crystal display, the residual strain is hardly alleviated.

The above-mentioned glass substrate for display refers to a raw plate used for a plasma display panel, a liquid crystal display panel, etc., and is used for a plasma display panel in the same size as the raw plate. There is also a case where a plurality of glass substrates for a liquid crystal display are formed in multiple from a single base plate.
Further, the “substrate surface” refers to a plane that is the front and back surfaces of a glass substrate that is a plate-like member, and “in the substrate surface” does not include the thickness direction of the glass substrate.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, strain and stress in a glass substrate are measured by the following methods. The distortion in the glass substrate can be estimated by measuring the optical birefringence, that is, by measuring the optical path difference between the orthogonal linearly polarized waves. Assuming that the optical path difference is R (nm), the deviation stress F generated due to the strain
(MPa) is expressed as F = R / CL. Here, L is the distance (c
m), and C is a proportionality constant determined by glass and is called a photoelastic constant, and is usually 20 to 40 (nm / cm) / (M
Pa).

When the glass has no strain, ie, no stress or isotropic stress, the two orthogonal linearly polarized waves pass through the glass at the same speed.
If there is a strain in the glass surface, the polarized wave will pass faster in the direction of compressive stress and will slowly pass in the direction of tensile stress. That is, an optical path difference occurs between two orthogonal linearly polarized waves. By taking an optical path perpendicular to the substrate surface and measuring the azimuth at which the optical path difference is maximized and its magnitude, the direction and magnitude of the strain in the glass substrate can be measured. The magnitude of this strain is defined as the deviation stress.

The deviation stress F is a stress value measured from an optical path difference of a polarized wave, and is an index indicating anisotropy of plane stress (ie, a difference between two principal stresses). The deviation stress F is an average value of the distance that the polarized light has passed in the glass substrate, and is determined as the direction in which the stress difference becomes maximum and the stress difference in any two axes orthogonal to each other in a plane perpendicular to the optical path. In the case where a compressive stress remains in a certain direction (for example, the X direction) in the surface of the glass substrate, and in the case where a tensile stress having the same magnitude remains in a direction perpendicular thereto (the Y direction), the deviation stress is measured. Have the same result. Further, if the same amount of compressive or tensile stress remains in two orthogonal axes directions (X direction and Y direction), the deviation stress becomes zero.

The measurement of glass strain using a linearly polarized wave is as follows.
The Senarmont method and the like are known, and an optical path difference of several tens nm can be detected. Conventionally, strain measurement of glass mainly targets a stress of several tens MPa remaining in tempered glass or the like, and the Senarmont method has sufficient analysis accuracy for such strain measurement.

However, the plane stress remaining on the glass substrate for a flat panel display is 0.1 MPa to 5 MPa.
It is a magnitude of MPa and cannot be sufficiently detected by the conventional measuring method. Therefore, the present inventors used an ABR-10A birefringence meter manufactured by Uniopt Corporation as a strain detection device. The ABR-10A birefringence measuring device is a device that measures a birefringent optical path difference and a principal axis direction by irradiating a transverse Zeeman laser beam and detecting a phase difference between orthogonal linearly polarized waves. The resolution has an optical path difference of 0.01 nm and a main axis azimuth of 0.1 degree.

[0026] Residual strain of the glass substrate occurs depending on the temperature distribution in the slow cooling step after forming the glass ribbon. That is, a compressive stress is formed in a portion that has been cooled earlier, and a tensile stress is formed in a portion that is cooled later. This is well known as the principle of physical strengthening or air cooling of glass. In the tempered glass, a compression stress layer is formed on the surface by rapidly cooling the glass surface.

Although tempered glass utilizes the stress distribution in the cross-sectional direction of the glass, glass also has a plane stress distribution. The present inventors have found that the distribution of plane stress of the glass substrate contributes to prevention of deflection and thermal warpage of the glass substrate, and to distribute stress remaining due to strain in the compression direction along the periphery of the substrate. As a result, it has become possible to provide a substrate in which deflection and thermal warpage are suppressed.

The distribution of the plane stress of the glass substrate is generated by the temperature distribution at the time of cooling after forming the glass ribbon. Generally, a glass substrate for a flat panel display is continuously manufactured by a manufacturing method such as a float method, a fusion method, and a slit down draw method. Therefore, the temperature distribution of the glass substrate during cooling is governed by the temperature distribution in the width direction perpendicular to the flow of the glass ribbon during manufacturing.

FIG. 1 schematically shows the temperature distribution in the width direction of the glass ribbon, the stress distribution of the glass substrate 1 cut out from the glass ribbon, and the deformation of the glass substrate due to cutting in the annealing step after the glass ribbon is formed. . Glass substrate 1
When the temperature of the peripheral portion is lower than that of the central portion, that is, in the state of FIG.
The glass substrate 1 cut from the glass ribbon is shown in FIG.
When the temperature of the peripheral portion of the glass substrate 1 is higher than that of the central portion, that is, in the state of (d) in the figure, tensile residual stress enters the peripheral portion and the glass substrate cut out from the glass ribbon 1, the plane stress state shown in FIG. Arrow 2 in the figure indicates the direction of the residual stress.

When there is a stress distribution in the flow direction of the glass ribbon, after the glass ribbon is cut to the size of the glass substrate, a stress distribution also occurs in the plate width direction. Hereinafter, this phenomenon will be described. The glass substrate 1 cut out from the glass ribbon in the stress state shown in FIGS.
Consider a case in which the glass ribbon is cut in a direction parallel to the flow of the glass ribbon and divided into two. The glass substrate 1 cut out from the glass ribbon is deformed into a fan shape to relieve the stress, and the glass substrate 1 cut out from the glass ribbon shown in FIG. 2B is cut out from the glass ribbon shown in FIG. The glass substrate 1 thus placed is in the state shown in FIG.

Here, it is assumed that the fan-shaped glass substrates (c) and (f) are bonded again to a rectangular shape as one original glass substrate. In this case, since the fan-shaped shape is corrected to the original rectangular shape, stress is generated not only in the cutting line direction but also in the direction perpendicular to the cutting line in the substrate plane. That is, when compressive or tensile residual stress is present near one side of a rectangular glass substrate, residual compressive or tensile stress (ie, conjugate stress) is also present near a side perpendicular to the side due to stress balance. appear. As a result of the above,
Plane residual stress generated in the glass substrate is distributed in a direction parallel to each side.

The present inventors have verified the relationship between the temperature distribution in the width direction of the glass ribbon 1 and the residual stress of the glass substrate.
By operating the above temperature distribution to the state shown in FIG. 1A, the stress distribution is changed to the state shown in FIG. 1B, that is, after cutting to the substrate size, the compressive stress is distributed in a direction parallel to each side. The substrate is manufactured.

Similarly, in order to control the residual stress of the glass substrate, it is also effective to perform a reheat treatment after forming the glass substrate. When performing the re-heat treatment, the glass substrate is heated to a temperature near the annealing point of the glass substrate while paying sufficient attention to the occurrence of deformation and scratches on the substrate, and the temperature of the central portion of the substrate is higher than the peripheral portion of the substrate. Maintain the condition and cool to near the strain point temperature.

Next, the strain point of glass will be described. The strain point is, as generally defined, a diameter of 0.65 mm,
When a load of 1 kg was applied to a glass fiber having a length of 460 mm and cooled at 4 ° C./min, the elongation was 0.0043.
mm / min, the viscosity is about 10
^{It is 14.5} dPa · s (10 ^13.5 Pa · s).

In the present invention, in the case of a glass substrate for a plasma display, the glass substrate preferably has a strain point of 570 ° C. or higher, and more preferably has a strain point of 590 ° C. or higher. Usually, in a plasma display manufacturing process, a heat treatment at 550 to 580 ° C. is performed. When the glass substrate is kept at a temperature exceeding the strain point for a long time, the residual strain is gradually relaxed. As a result, the effect of reducing the deflection and thermal warpage of the stress remaining in the substrate cannot be exerted in the subsequent processes. Therefore,
The strain point of the glass substrate is preferably higher than the heat treatment temperature in the display manufacturing process.

When the heat treatment temperature in the plasma display manufacturing process is higher than the strain point of the glass substrate, an effect of reducing deflection and thermal warpage due to residual stress can be expected at least up to the corresponding heat treatment process. In particular, thermal warpage
Since it occurs at the beginning of the heating step, even in the heat treatment step at a temperature higher than the strain point, the effect of reducing the warpage due to the residual stress appears.

In the present invention, in the case of a glass substrate for a liquid crystal display, particularly a glass substrate for a polysilicon type liquid crystal display, the glass substrate preferably has a strain point of 650 ° C. or more, and has a strain point of 665 ° C. or more. Is more preferable. Usually, in a manufacturing process of a polysilicon type liquid crystal display, 500 to 65
A heat treatment at 0 ° C. is performed. As described above, the effect of the residual stress disappears when the heat treatment temperature exceeds the strain point.
In general, a thin substrate having a thickness of 0.7 mm or less is used in a liquid crystal display, so that the strain due to the heat treatment can be alleviated more quickly. Therefore, the strain point is 10 times higher than the heat treatment temperature.
It is preferable that the temperature is higher by at least C.

Even when the heat treatment temperature in the manufacturing process of the liquid crystal display is higher than the strain point of the glass substrate, the effect of reducing deflection and thermal warpage due to residual stress can be expected at least up to the corresponding heat treatment process.

Next, the residual stress measured optically will be described. The optically measured residual stress is
More precisely, it is a deviation stress. That is, the stress difference in two directions orthogonal to each other in a plane perpendicular to the optical axis is measured.
In the peripheral portion of the glass substrate, since the substrate is cut at the side, no stress is applied in a direction perpendicular to the side, and a stress due to strain remains only in a direction parallel to the side. Therefore, the deviation stress near the side becomes substantially equal to the residual stress. On the other hand, the stress due to strain is applied to the deviation stress in the central portion of the substrate from all directions in the plane and is relatively canceled in the orthogonal direction. Therefore, a value smaller than the true residual stress is measured.

In the glass substrate of the present invention, compressive stress is distributed in a direction along the periphery of the substrate within the plane of the substrate. At the periphery of the substrate, the measured deviation stress is a value close to the true residual stress, while at the center of the substrate, the stress distribution is pulled from all sides, but apparently near the center, , A small deviation stress will be observed.

The inventors of the present invention have proposed a display glass substrate in which the deviation stress in the substrate plane measured in the thickness direction due to the residual strain in the substrate is distributed in the compression direction along the periphery of the substrate. And that heat warpage hardly occurs.

When the area of the substrate is small, even if deflection or thermal warpage occurs, the deformation amount is small, so that there is substantially no problem. When the board dimensions are rectangular, the short side is 300 mm or more,
More remarkably, when the short side is 500 mm or more, the amount of deformation due to deflection or thermal warpage increases, so that deformation suppression due to residual stress is effective.

When the substrate size is rectangular, the deviation stress in the glass substrate having a short side of 300 mm or more is distributed along the periphery of the substrate in the compression direction, and the deviation compression stress in the direction parallel to the side near each side. When the maximum value is 0.3 MPa or more, the effect of suppressing the deflection and thermal warpage of the substrate appears.

In the case of a substrate having a rectangular shape with a short side of 500 mm or more, the internal stress generated by deflection or thermal warpage becomes larger. Therefore, the maximum value of the deviation compressive stress along the periphery for suppressing the internal stress is: It is preferably 0.5 MPa or more, and more preferably 1 MPa or more in order to exhibit a more remarkable effect. However, even if the value of the deviation compressive stress becomes too large, the glass substrate buckles to cause complicated deformation, so that it is not practical and has a certain upper limit. If the short dimension of the substrate exceeds 3,000 mm in a rectangular shape, handling of the glass substrate becomes difficult due to the problem of weight and deflection of the substrate, which is not practical. Therefore, there is no point in controlling deflection and thermal warpage with residual stress. .

When the thickness of the glass substrate is less than 0.3 mm, deflection and thermal warpage are more likely to occur. It is not practical because it yields and causes complicated deformation. When the thickness of the glass substrate exceeds 6 mm, since there is a sufficient thickness, deflection and thermal warpage hardly occur, and there is no point in controlling the residual stress.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The amount of deflection of a glass substrate is determined by the density of the glass, the modulus of longitudinal elasticity of the glass, the dimensions of the glass substrate, the method of supporting the substrate, and the like. The present invention provides a glass substrate in which the deflection is reduced by utilizing the residual stress in the glass substrate with respect to these factors. On the other hand, thermal warpage is affected by the thermal conductivity, specific heat, thermal expansion coefficient, and the like of glass, in addition to the physical properties described above. The thermal warpage can also be reduced by utilizing the residual stress in the glass substrate.

In this embodiment, the density was 2.50 g / cm
^Two, Longitudinal elastic modulus 77 GPa, thermal conductivity 1.0 W / (m ·
℃), specific heat 750J / (kg ・ ℃), coefficient of thermal expansion 38 ×
10 ^-7/ ° C, photoelastic constant 30 (nm / cm) / (MP
The glass substrate of a) was used. Glass substrate is float method
Is formed into a thickness of 0.7 mm, and
Then, it becomes rectangular 550mm long dimension × 650mm long side
I cut it out. At this time, the short side is the width direction of the glass ribbon,
The long side was set in the flow direction of the glass ribbon.

During the production of the test glass substrate, the glass substrate is produced by operating the heater in the annealing step so as to change the relationship between the center and both ends in the temperature distribution in the width direction of the glass ribbon. did. When manufacturing a substrate with little residual distortion, the temperature distribution in the width direction of the plate was made uniform.
When manufacturing a substrate in which compressive stress remained along the periphery, the temperature of the central portion of the substrate was adjusted so as to be higher than that of both ends, and cooling was performed from both ends first.

The deviation stress was measured using the above-mentioned ABR manufactured by Uniopt.
Using a -10A birefringence measuring instrument, it was determined by conversion from the optical path difference of birefringence. Measurements were taken at 50 mm intervals in the vertical and horizontal directions.
The test was performed for a total of 143 points on one glass substrate.

The substrate on which the stress was measured was measured for deflection in a state where two sides were supported. 2 parallel on the platen with an interval of 600mm
Two support rods were provided, and the glass substrate was placed on the two support rods with the 550 mm side of the glass substrate parallel to the support rods. Raise and lower the support rods in parallel, stop raising and lowering the support rods at the moment when the center of the bent substrate comes into contact with the surface plate, measure the height difference between the surface of the surface plate and the upper end of the support rods at that time, and measure the amount of deflection. And The results are shown in Table 1 as "actual deflection amount".

Next, the amount of thermal warpage of the glass substrate was evaluated using a hot plate having an area of 600 mm × 700 mm.
A glass substrate at room temperature is quickly settled on a hot plate heated to a predetermined temperature, and the lift amount of four corners of the substrate after 5 minutes of standing is measured by setting a scale (gold scale) vertically on the hot plate. did. The “lift amount” shown in FIG. 7, which is the measurement result, will be described later.

[0052]

[Table 1]

Table 1 shows the measured direction of the deviation stress near the periphery of the substrate, the maximum stress in the substrate surface, and the amount of deflection measured. Samples 1 to 3 are in a state in which the temperature of the central portion of the glass ribbon is higher than the peripheral portion, Sample 4 is in a state in which the temperature distribution is flat in the width direction of the glass ribbon, and Sample 5 is in the state of the glass ribbon. The cooling was performed in a state where the temperature at the center was lower than that at the periphery. The measurement results of the deviation stress of each substrate are shown in FIGS.

FIGS. 2 to 6 show ABR-10 manufactured by Uniopt.
A The result of measurement with a birefringence meter, the center of each circle indicates the measurement point, the diameter of the circle is the magnitude of the deviation stress, the direction drawn by the line drawn as the diameter of the circle is the relative tensile stress, the diameter And the vertical direction on the paper indicates the direction in which the compressive stress becomes relatively large. 2 to 4, it can be seen that the line having the circular diameter is directed toward the center of the glass substrate, and the periphery of the glass substrate is in the compression direction. On the other hand, in FIG. 6, the line having the circular diameter runs around the periphery of the substrate, and it can be seen that the periphery of the glass substrate is in the tensile direction.

Since the glass ribbon is manufactured continuously,
At the time of cooling the glass ribbon, a temperature distribution is formed only in the central part and the peripheral part of the sheet width only in the sheet width direction, and the temperature distribution simply drops from upstream to downstream in the flow direction of the glass ribbon. I have. However, as explained above,
After being cut out to the size of the glass substrate due to the balance of stress, the stress distribution is in a direction parallel to each side with respect to the glass substrate.

The amount of deflection of the glass substrate is strongly affected by the thickness deviation. Therefore, the thickness of the substrate was measured, and the effect was estimated. The plate thickness in Table 1 is an average value measured ten times for each substrate.

In Table 1, Samples 1 to 3 are substrates in which residual stress due to strain is in a state of compression in the surroundings, and the amount of deflection is smaller than the value calculated from the sample shape in which the thickness has been corrected. On the other hand, the sample 5 is a substrate in which the residual stress due to the strain is in a peripheral tensile state, and the deflection amount is larger than a value calculated from the sample shape in which the thickness is corrected. Sample 4
Shows that the residual stress due to strain is extremely small, and the amount of deflection matches the value calculated from the sample shape. The “deflection amount calculated from the plate thickness” is a value calculated by the equation of the beam and the deflection of the material mechanics. Specifically, the maximum deflection amount of the simple beam due to the uniformly distributed load (the center position of the beam) The deflection amount was calculated by substituting various amounts into the equation.

The glass substrate at room temperature was left on a hot plate, and after 5 minutes, the result of measurement of the amount of thermal warpage on the hot plate is shown in FIG. The temperature in FIG. 7 is the set temperature of the hot plate, and the lift amount is an average value measured at four corners of the glass substrate. In the substrate in a compressed state around the samples 1 to 3, the warpage, that is, the rising start temperature is high, and the rising amount at the same temperature is small. That is, it can be seen that in the glass substrate in which the compressive stress is distributed along the periphery, both the deflection and the thermal warpage are reduced.

[0059]

According to the present invention, deflection and thermal warpage of a glass substrate can be reduced. With the glass substrate of the present invention, troubles such as cracking during transportation and manufacturing process of a flat panel display can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a temperature distribution diagram of a glass ribbon in a plate width direction, a stress state diagram of a glass substrate cut out from the glass ribbon, and a deformation due to cutting of the glass substrate. (B) is the stress distribution of the glass substrate cut out from the glass ribbon of (a), (c) is the deformation of the glass substrate caused by cutting, and (D) is the temperature distribution in the width direction of the glass ribbon before cutting, and (e) is
(D) shows the stress distribution of the glass substrate cut out from the glass ribbon, and (f) shows the deformation due to the cutting of the glass substrate of (e).

FIG. 2 is a diagram illustrating an example of measuring a deviation stress of a glass substrate whose surroundings are compressive stress.

FIG. 3 is a diagram showing an example of measuring a deviation stress of a glass substrate whose surrounding is a compressive stress.

FIG. 4 is a diagram showing an example of measuring a deviation stress of a glass substrate whose surroundings are compressive stress.

FIG. 5 is a diagram showing an example of measuring a deviation stress of a glass substrate having an extremely small stress distribution.

FIG. 6 is a diagram showing an example of measuring a deviation stress of a glass substrate whose periphery has a tensile stress.

FIG. 7 is a diagram showing a result of a measurement of a warpage on a hot plate.

[Explanation of symbols]

 1: glass substrate 2: direction of residual stress

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G015 EA03 5C040 GA01 GA09 GA10 KA07 KB11 MA09 MA10 MA23

Claims (3)

[Claims] 1. A glass substrate having a substantially rectangular surface shape with a short side of 300 mm or more and a plate thickness of 0.3 mm or more and 6 mm or less, measured in a plate thickness direction by residual strain in the glass substrate. The deviation stress in the plane of the substrate at the time of distribution is distributed in the compression direction along the periphery of the substrate, and the maximum value of the deviation compression stress in the direction parallel to the side near each side is 0.3 MPa or more. substrate. 2. The display glass substrate according to claim 1, which has a strain point of 570 ° C. or higher and is used for a plasma display panel. 3. The display glass substrate according to claim 1, which has a strain point of 650 ° C. or higher and is used for a liquid crystal display panel.