JP2012128435A - Glass substrate for display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass substrate for display in which substrate deformation generated in cutting is suppressed, thereby preventing pattern deviation in laminating.SOLUTION: A glass substrate has a nearly rectangular plane shape with a short side of 300 mm or more and a long side of 3000 mm or less, and a thickness of 0.3 mm or more and 6 mm or less. In the glass substrate for display used for high-definition, a deviatoric stress in the substrate plane, due to residual strain within the glass substrate, measured in the direction of thickness is 0.3 MPa or less at all positions in the substrate, and a photoelasticity constant is 20 to 40 (nm/cm)/(MPa). Further, the maximum deformation, after patterns of multiple planes are formed in one sheet of the substrate and cut in half, is 2.6 μm or less in the case of stress in a compression direction along the periphery and 1.9 μm or less in the case of stress in a tension direction along the periphery.

Description

  The present invention relates to a glass substrate for display, and in particular, a liquid crystal display (TFT-LCD, STN-LCD), a plasma display (PDP), a plasma assisted liquid crystal display (PALC), an electroluminescence display (EL), a field The present invention relates to a glass substrate for flat panel displays (a general term for flat displays) such as an emission display (FED).

  In a flat panel display, usually two glass substrates are used. These glass substrates are called an array side substrate and a color filter side substrate in a TFT liquid crystal display, and a front plate and a back plate in a plasma display. The present invention relates to these glass substrates.

  A flat panel display normally uses two glass substrates, and a light emission mechanism and a light transmission control mechanism are formed between the two glass substrates. Typical examples of the glass used as the glass substrate include non-alkali borosilicate glass (for example, manufactured by Asahi Glass Co., Ltd. [trade name: AN635, AN100, etc.) for TFT liquid crystal displays, and soda lime glass (for STN liquid crystal displays). For example, high strain point glass (for example, [trade name: PD200] manufactured by Asahi Glass Co., Ltd.) or the like is used in plasma displays.

  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 of a predetermined dimension and supplied as a glass substrate. Some glass substrates are subjected to a slow cooling treatment (annealing treatment) for the purpose of controlling the heat shrinkage rate (compaction) to a constant value after molding.

  In the manufacture of a flat panel display using the above glass substrate, multiple chamfering may be performed in order to increase production efficiency. That is, a plurality of patterns for a panel such as two surfaces, four surfaces, six surfaces, and eight surfaces are formed in one glass substrate, and a plurality of panels are manufactured at the same time. A panel on which a pattern of a plurality of surfaces is formed is cut into a size corresponding to one surface before or after the bonding of the two substrates, and becomes the size of the product panel.

JP-A-5-339021 JP-A-5-163032

  In the multi-planar substrate, if a strain in the plane direction exists in the glass substrate, the deformation as shown in FIG. 1 occurs due to cutting. Here, the arrow 2 in the figure indicates the direction of residual stress. That is, FIG. 1 is a schematic diagram for explaining deformation due to cutting of the glass substrate 1, (a) is a schematic diagram for explaining the state of residual stress of the glass substrate 1 before cutting, and (b) is ( The schematic diagram which shows the shape after cut | disconnecting the glass substrate 1 of a), (c) is a schematic diagram explaining the state of the residual stress of the glass substrate 1 before cutting | disconnection, (d) is the glass substrate of (c). It is a schematic diagram which shows the shape after cut | disconnecting.

  When such deformation occurs, a deviation occurs in the formed pattern when the two glass substrates are bonded to each other. However, such a deviation of the pattern is a quality problem. For example, in the manufacturing process of a TFT liquid crystal display, display unevenness due to a decrease in luminance occurs due to a pattern shift of several μm to several tens of μm.

  The deformation of the glass substrate due to the cutting depends on the size of the glass substrate, and the glass substrate having a larger planar dimension is more conspicuous. That is, when the strain is uniformly distributed in the plane of the glass substrate, the residual stress increases as the plane dimension of the glass substrate increases. In addition, when a certain shape is deformed (similar shape), the amount of deformation at the periphery of the substrate increases as the planar dimension of the glass substrate increases. In particular, the deformation of the glass substrate due to cutting is a problem that occurs remarkably in a rectangular glass substrate having a short side of 300 mm or more.

  Here, the relationship between the distortion of the glass substrate and the warp of the glass substrate will be described. The glass substrate is distorted inside due to the thermal history during cooling, and residual stress is generated. Physically tempered glass is known as a glass using this phenomenon. That is, it is a method of forming a compressive stress layer on the glass surface by blowing air or the like on the surface when the glass is cooled and forcibly cooling the surface.

  The distortion of the glass occurs not only in the stress distribution in the cross-sectional direction of the glass known as tempered glass but also in the plane direction. That is, when the temperature of the peripheral portion is lower than that of the central portion of the glass substrate when the glass substrate is cooled, stress in the compression direction is generated along the periphery within the glass substrate surface. Conversely, when the temperature of the peripheral part is higher than that of the central part during cooling of the glass substrate, a stress in the tensile direction is generated along the periphery in the glass substrate surface.

  FIG. 1 described above schematically shows the deformation of the substrate that occurs when the substrate in which the stress due to the strain remains is cut. In the substrate where compressive stress is applied to the periphery, the substrate is deformed inward because the compressive strain is released and stretched after cutting (the state shown in FIG. 1B). In the substrate where tensile stress is applied to the surroundings, the substrate is deformed to the outside because the tensile strain is released and contracts after cutting (the state shown in FIG. 1D).

  As described above, when a strain exists in the glass substrate, the substrate is deformed at the time of cutting. Therefore, there has been a demand for a glass substrate having no strain or a glass substrate having a certain value or less that does not deform the substrate.

The present invention is a glass substrate having a substantially rectangular surface shape with a short side of 300 mm or more and a long side of 3000 mm or less, and a plate thickness of 0.3 mm or more and 6 mm or less, due to residual strain in the glass substrate, The deviation stress in the substrate surface when measured in the thickness direction is 0.3 MPa or less at all positions in the substrate, and the photoelastic constant is 20 to 40 (nm / cm) / (MPa). The maximum deformation after a multi-surface pattern is formed on a single substrate and cut in half is 2.6 μm or less when the stress direction is ambient compression, and 1 when the stress direction is ambient tension. Provided is a glass substrate for display for high-definition applications having a size of .9 μm or less.
Such a glass substrate having a small deviation stress due to residual strain in the substrate is desirable as a glass substrate for a display because the substrate is not deformed during cutting or almost negligible.
In addition, the glass substrate of this invention is a substantially rectangular thing, and includes the glass substrate which cut off the corner of the peripheral part (corner cut).

In the present invention, after being cut into a substantially rectangular surface shape, a heat treatment of heating / slow cooling may be performed.
Even if the glass substrate is not desirable as a glass substrate for a display because the residual stress due to the residual strain in the substrate is large, the stress due to the residual strain in the substrate can be reduced by performing such processing.

  In the present invention, if the manufacturing conditions at the time of molding the glass substrate are optimized and a glass substrate having a small deviation stress due to residual strain in the substrate can be manufactured, heating / annealing heat treatment is unnecessary, which is most desirable.

Moreover, this invention provides the glass substrate for a display used for a liquid crystal display panel whose short side is 500 mm or more and plate | board thickness is 1.1 mm or less.
In the liquid crystal display panel, a glass substrate having the above-mentioned plate thickness is usually used. With such a plate thickness, distortion is not easily generated in the molding process, and heating / annealing heat treatment is unnecessary.

The present invention also provides a glass substrate for display having a short side of 500 mm or more and a plate thickness of 1.5 mm or more and used for a plasma display panel.
For the plasma display panel, a glass substrate having the above thickness is usually used. With such a plate thickness, heating / slow cooling heat treatment is effective in reducing residual strain in the substrate.

  According to the present invention, the amount of deformation when the glass substrate is cut can be controlled within a range that does not cause a problem. In the present invention, when a flat panel display is manufactured, a multi-surface pattern forming a pattern of a plurality of surfaces in one substrate can be easily performed.

It is a schematic diagram explaining the deformation | transformation by the cutting | disconnection of a glass substrate, Comprising: (a) is a schematic diagram explaining the state of the residual stress of the glass substrate before cutting | disconnection, (b) cut | disconnected the glass substrate of (a). The schematic diagram which shows the shape after the cutting | disconnection, (c) is a schematic diagram explaining the state of the residual stress of the glass substrate before a cutting | disconnection, (d) is the schematic diagram which shows the shape after cut | disconnecting the glass substrate of (c). . It is a schematic diagram of the temperature distribution of the width direction of a glass ribbon, and the stress distribution of the cut-out glass substrate, (a) is a temperature distribution when the temperature of a peripheral part is higher than a center part, (b) is (a ) Is a schematic diagram for explaining the state of residual stress after cutting the glass ribbon, (c) is a temperature distribution when the temperature of the peripheral portion is lower than the central portion, and (d) is the glass ribbon of (c). It is a schematic diagram explaining the state of the residual stress after cut | disconnecting. It is a figure which shows the example of deviation stress measurement of the glass substrate whose circumference | surroundings are compressive stress. It is a figure which shows the example of deviation stress measurement of the glass substrate whose circumference | surroundings are tensile stress. It is a figure which shows the modification by the cutting | disconnection of the glass substrate whose periphery is a compressive stress. It is a figure which shows the modification by the cutting | disconnection of the glass substrate whose periphery is a tensile stress.

In the present invention, strain and stress in the glass substrate are measured by the method described below.
The strain in the glass substrate can be estimated by measuring optical birefringence, that is, by measuring the optical path difference of orthogonal linearly polarized waves. When the optical path difference is R (nm), the deviation stress F (MPa) generated by the strain is
F = R / CL
Represented as: Here, L is the distance (cm) through which the polarized wave has passed, and C is a proportional constant determined by the glass, which is called a photoelastic constant, and is usually 20 to 40 (nm / cm) / (MPa).

  When the glass is not distorted, i.e. when there is no stress or isotropic stress, the two orthogonal linearly polarized waves pass through the glass at the same speed. When there is distortion in the glass surface, the polarized wave passes fast in the direction of compressive stress, and the polarized wave passes slowly in the direction of tensile stress. That is, an optical path difference is generated between two orthogonal linearly polarized waves. By taking an optical path perpendicular to the substrate plane and measuring the direction and magnitude of the optical path difference at the maximum, the directionality and magnitude of strain in the glass substrate can be measured. This value is defined as the deviation stress.

  The deviation stress F is a stress value measured from the optical path difference of the polarized wave and serves as an index representing the anisotropy of the stress existing in the plane. The deviation stress F is an average value of the distance through which the polarized light has passed through the glass substrate, and is obtained as the stress difference direction and the stress difference direction in any two axes orthogonal to each other in a plane perpendicular to the optical path. Measurement of deviation stress when compressive stress remains in a certain direction (for example, X direction) in the glass substrate surface and when tensile stress of the same magnitude remains in a direction perpendicular to it (Y direction) Give the same result. In addition, if the same amount of compressive or tensile stress remains in two orthogonal directions (X direction and Y direction), the deviation stress becomes zero.

  Senalmon method or the like is known for measuring strain of glass using a linearly polarized wave, and an optical path difference of several tens of nm can be detected. Conventionally, strain measurement of glass has mainly been directed to stress of several tens of MPa remaining in tempered glass or the like, and the Senarmon method has sufficient analysis accuracy for such strain measurement.

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

  The residual strain of the glass substrate is generated depending on the temperature distribution in the slow cooling 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 has been cooled later. This is well known as the principle of physical strengthening or air cooling strengthening of glass. In tempered glass, a compressive stress layer is formed on the surface by rapidly cooling the glass surface.

  The tempered glass uses the stress distribution in the thickness direction of the glass, but the glass also has a stress distribution in the plane direction. The present inventors have found that a substrate in which the stress distribution in the plane direction of the glass substrate causes deformation during glass cutting and that the deformation is suppressed by controlling the residual stress due to strain to a certain value or less. I found out that I could get it.

  The stress distribution in the plane direction of the glass substrate is generated by the temperature distribution during cooling after forming the glass ribbon. In general, a glass substrate for a flat panel display is continuously manufactured by a manufacturing method such as a float method, a fusion method, or a slit down-draw method. Therefore, it is governed by the temperature distribution during cooling, particularly the temperature distribution in the plate width direction perpendicular to the flow of the glass ribbon during production.

  In FIG. 2, the temperature distribution of the plate | board width direction of a glass ribbon and the stress distribution of the cut-out glass substrate 1 are shown typically. Here, the arrow 2 in the figure indicates the direction of residual stress. When the temperature of the peripheral part is lower than that of the central part, that is, in the state of (a) in the figure, the residual stress of compression enters the state of the peripheral part and becomes the state of (b) in the figure, and the temperature of the peripheral part is compared with the central part. When it is high, that is, when it is in the state of (c) in the figure, the tensile residual stress enters the peripheral portion, and the state of (d) in the figure is reached.

  The present inventors verified the relationship between the temperature distribution of the glass ribbon in the plate width direction and the residual stress of the glass substrate, and found the condition that the residual stress of the glass substrate becomes extremely small by manipulating the temperature distribution.

  In order to reduce the residual stress of the glass substrate, it is effective to perform an annealing process of the substantially rectangular glass substrate cut out to a predetermined size, that is, a reheating / annealing heat treatment process in the glass substrate manufacturing process. is there. As described above, when the annealing treatment is performed on the glass substrate, it is necessary to pay close attention to the deformation of the substrate and the generation of scratches, and heat the glass substrate to near the annealing point temperature, and gradually cool it to near the strain point temperature. Can be done.

  Generally, there are many large plasma display panels of 50 type (diagonal approximately 1270 mm) or more, and the size of the glass substrate used for display is large and the plate thickness is also large. Therefore, distortion is likely to occur in the plate glass forming process, and there is an effect of performing an annealing process after forming the glass substrate. However, as described above, the residual stress of the glass substrate can be extremely reduced by manipulating the temperature distribution in the annealing process at the time of forming the glass substrate, and the annealing process after forming the glass substrate can be made unnecessary.

  On the other hand, since the liquid crystal display panel has a strong demand for weight reduction, the thickness of the glass substrate for display used is generally small. Therefore, distortion hardly occurs in the molding process, and there is little need to perform an annealing process after the glass substrate is molded.

  From the standpoint of production cost, it is preferable not to perform the annealing process after the glass substrate molding because it leads to an increase in cost. When the annealing treatment is not performed after the glass substrate is formed, a horizontal drawing method such as a float method, which can ensure a long slow cooling zone when the glass substrate is formed, is preferable.

  As described above, the optically measured residual stress is precisely 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 part of the glass substrate, since the substrate is cut at the side, the stress in the direction perpendicular to the side does not act, and the stress due to strain remains only in the direction parallel to the side. Therefore, the deviation stress in the vicinity of the side is substantially equal to the residual stress. On the other hand, since the stress due to strain is applied from all directions within the plane and the relative stress is canceled in the orthogonal direction, the deviation stress at the center of the substrate is measured to be smaller than the true residual stress. Therefore, in the present invention, the deviation stress is measured, for example, at intervals of 50 mm vertically and horizontally within the surface of the glass substrate, and the maximum value of the deviation stress at all measurement points is used as an index.

  As a result, it has a substantially rectangular surface shape with a short side of 300 mm or more and a long side of 3000 mm or less, and a plate thickness of 0.3 mm or more and 6 mm or less, measured in the plate thickness direction due to residual strain in the substrate. When the deviation stress in the surface of the substrate is measured by an optical method by applying light, when it is 1 MPa or less at all positions in the substrate, more preferably 0.6 MPa or less, high-definition use It has been found that the amount of deformation due to cutting is small enough not to cause a practical problem when the glass substrate is 0.3 MPa or less.

  When the substrate area is small, the amount of deformation due to the residual stress is small, so that even if deformation occurs, there is no substantial problem. When the substrate size is rectangular and the short side is 300 mm or more, and more notably, the short side is 500 mm or more, the amount of deformation becomes large, so that the residual stress must be controlled. When the substrate size is rectangular and the short side exceeds 3000 mm, handling of the glass substrate becomes difficult and impractical due to problems of weight and substrate deflection, so there is no point in controlling residual stress.

  When the thickness of the glass substrate is less than 0.3 mm, a decrease in the strength of the glass substrate and an increase in deflection are problematic and are not practical. In a large display substrate such as a plasma display panel of 30 type (diagonal approximately 762 mm) or more, the plate thickness is preferably 1.5 mm or more from the viewpoint of strength. When the plate thickness exceeds 6 mm, the glass substrate is too heavy, which is not suitable. In applications where weight reduction is important, such as liquid crystal displays, the plate thickness is preferably 1.1 mm or less. Therefore, 1.5 mm or more and 6 mm or less are preferable for applications such as a plasma display, and 0.3 mm or more and 1.1 mm or less are preferable for applications such as a liquid crystal display.

The amount of deformation caused by cutting the glass substrate depends on the size of the glass substrate, the cutting position, the residual stress in the glass substrate, and the longitudinal elastic modulus of the glass. In the following, a glass substrate having a longitudinal elastic modulus of 7500 kg / mm ² and a photoelastic constant of 27.6 (nm / cm) / (MPa) was used. The glass substrate was formed into a thickness of 0.7 mm by a float method, and was cut into a rectangular size of 550 mm × 670 mm as a test glass substrate. At this time, the side of 550 mm was in the plate width direction of the glass ribbon, and the side of 670 mm was in the flow direction of the glass ribbon.

During the production of the test glass substrate, the glass ribbon was operated so that the temperature distribution in the plate width direction was as uniform as possible so that the residual stress due to strain was reduced.
The deviation stress was obtained by converting from the optical path difference of birefringence using the above-mentioned ABR-10A birefringence measuring device manufactured by UNIOPT. The measurement was carried out on a total of 143 points on a single glass substrate at intervals of 50 mm in the vertical and horizontal directions.

  A black matrix for a color filter was formed on the glass substrate on which the stress was measured, and the positions of the corners of the black matrix were measured with a precision length measuring device (UMIC800 manufactured by Socia). Specifically, six rectangular patterns (size: 244.494 mm × 183.893 mm) were formed on the glass substrate, and the X and Y coordinates of the vertices of each rectangle were measured. The arrangement of the rectangles is the positional relationship shown in FIGS. 5 and 6, and the interval between adjacent rectangles is 27 mm in both the X and Y directions.

  The glass substrate was cut in half in a direction parallel to the side of 670 mm, that is, cut into a size of 275 mm × 670 mm, the corner portion of the black matrix was measured again, and the amount of deformation before and after cutting was evaluated.

  Table 1 shows the direction and maximum stress of the deviation stress of the substrate measured, and the direction of deformation and the maximum deformation after cutting. The optical path difference is also shown. In the table, samples 1 to 6 are examples, and sample 7 is a comparative example. That is, Samples 1 to 6 are samples controlled so that the temperature distribution in the plate width direction of the glass ribbon is as uniform as possible. Among these samples, it is estimated that the samples 1 to 3 have a slightly higher temperature at the center of the glass ribbon than the periphery, and samples 4 to 6 have a slightly lower temperature at the center of the glass ribbon than the periphery. .

試料１〜３のガラス基板は、周囲に沿って圧縮方向の応力分布を有しており、切断により圧縮部分が開放されて伸びるため、内側へ変形している。一方、試料４〜６のガラス基板は、周囲に沿って引張方向の応力分布を有しており、切断により引張部分が開放されて縮むため、外側へ変形している。試料１と４の基板について偏差応力の測定結果をそれぞれ図３と図４に、切断後の変形挙動をそれぞれ図５と図６に示す。

The glass substrates of Samples 1 to 3 have a stress distribution in the compression direction along the periphery, and are deformed inward because the compression portion is opened and stretched by cutting. On the other hand, the glass substrates of Samples 4 to 6 have a stress distribution in the tensile direction along the periphery, and are deformed to the outside because the tensile portions are opened and contracted by cutting. The measurement results of the deviation stress for the substrates of Samples 1 and 4 are shown in FIGS. 3 and 4, respectively, and the deformation behavior after cutting is shown in FIGS. 5 and 6, respectively.

  FIG. 3 and FIG. 4 are the results of measurement using an ABR-10A birefringence measuring instrument manufactured by UNIOPT Co., Ltd., where the center of each circle indicates the measurement point, the length of the circle diameter is the magnitude of the deviation stress, and the diameter of the circle. The direction in which the drawn line is relatively tensile stress, and the direction perpendicular to the diameter line is the direction in which it is relatively compressive stress. In FIG. 3, it can be seen that the circle diameter line faces the center of the glass substrate, and the periphery of the glass substrate is in the compression direction. On the other hand, FIG. 4 shows that the circle diameter line rotates around the periphery of the substrate, and the periphery of the glass substrate is in the tensile direction.

  FIG. 5 and FIG. 6 show the results of measurement using the above-described precision length measuring machine (UMIC800 manufactured by Sokkia). The units of the X and Y axes are both mm and indicate the positional relationship between the rectangles as described above, but the displacement is smaller than the size of the glass substrate and the rectangle, so that the displacement is easy to distinguish. Only the amount is displayed with the difference before and after cutting magnified 10,000 times.

  5 and 6, the measurement point at the lower left corner of the lower left rectangle is fixed, and the direction of the side (X coordinate) whose length is 275 mm from the fixed point is set as the stationary direction. The amount of displacement is displayed. The glass substrate having a stress distribution in the compressive direction along the periphery is deformed inside (FIG. 5), and the glass substrate having a stress distribution in the tensile direction along the periphery is deformed outward (FIG. 6). Yes.

  The glass substrate of Sample 7 in Table 1 is a comparative example, and is a glass substrate in which a tensile stress is generated around the glass ribbon by slowly cooling while heating both ends of the glass ribbon in the width direction of the glass ribbon. It is. The stress of 1 MPa or more remains at the maximum, and the deformation amount is extremely large as 12.6 μm.

1 Glass substrate before cutting 2 Direction of residual stress 3 Glass substrate after cutting

Claims (6)

A glass substrate with a short side of 300 mm or more and a long side of a substantially rectangular surface shape of 3000 mm or less, and a plate thickness of 0.3 mm or more and 6 mm or less,
The deviation stress in the substrate surface due to residual strain in the glass substrate when measured in the thickness direction is 0.3 MPa or less at all positions in the substrate, and the photoelastic constant is 20 to 40 (nm / cm). / (MPa), the maximum deformation after a multi-plane pattern is formed in one substrate and cut in half is 2.6 μm or less when the stress direction is ambient compression, and the stress direction is A glass substrate for display for high-definition applications having a peripheral tension of 1.9 μm or less. The short side is 500 mm or more, the plate thickness is 1.1 mm or less,
The glass substrate for display according to claim 1, which is used for a liquid crystal display panel. The short side is 500 mm or more, the plate thickness is 1.5 mm or more,
The glass substrate for display according to claim 1, which is used for a plasma display panel.   The glass substrate for display according to claim 2, wherein the glass used is alkali-free glass and is for TFT-LCD.   The glass substrate for a display according to claim 3, wherein the glass used is a high strain point glass.   6. For a display according to any one of claims 1 to 5, wherein a plurality of patterns for two, four, six or eight panels are formed in one glass substrate. Glass substrate.

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