WO2010104039A1 - Glass substrate and method for manufacturing same - Google Patents

Abstract

Provided is a glass substrate (1) having the front surface (2a), the rear surface (2b), and the edge surface (3b) between the outer circumferential ends of the both surfaces (2a, 2b). A chamfered surface (4) is formed on the boundary section between the front surface (2a) and/or the rear surface (2b) and the edge surface (3b), the ten-point average roughness (Rz₂) of the chamfered surface (4) is smaller than the ten-point average roughness (Rz₁) of the edge surface (3b), and the average length (RSm₂) of the roughness curve elements of the chamfered surface (4) is longer than the average length (RSm₁) of the roughness curve elements of the edge surface. Preferably, the ten-point average roughness (Rz₂) of the chamfered surface (4) and the ten-point average roughness (Rz₁) of the edge surface (3b) satisfy the inequalities of Rz₁≤1.5 and 1.5≤Rz₁/Rz₂≤10.0.

Description

Glass substrate and manufacturing method thereof

The present invention relates to a glass substrate formed by optimizing the surface properties of a boundary portion between a front surface and a back surface and end surfaces existing between outer peripheral ends of both surfaces, and a manufacturing method thereof.

As is well known, image (video) display devices in recent years are flat panel displays (FPD) represented by a liquid crystal display (LCD), a plasma display (PDP), a field emission display (FED), an organic EL display (OLED), and the like. ) Is the mainstream. In addition, organic EL is being used as a planar light source such as a backlight of an LCD or a light source for indoor lighting by causing only three colors (for example, white) to emit light without causing the three primary colors to be flickered by a TFT unlike OLED.

These FPDs and illuminations are each configured by attaching and combining various components including respective elements and wirings on the surface of the glass substrate. In particular, from the viewpoint of improving productivity, FPD is formed by forming a plurality of FPD panel elements on a single large glass substrate, and finally dividing them appropriately to obtain individual FPD glass panels. So-called multi-taking is performed. Since this multi-collection improves the efficiency as the glass substrate becomes larger, a glass substrate having a side length of more than 3 m has been used. Further, in recent years, since the size of the FPD itself has been promoted, a thinner glass substrate is required to meet the demand for preventing the increase in weight. Moreover, this kind of glass substrate has come to be used as a glass substrate for solar cells in addition to the above-mentioned FPD and organic EL illumination.

And in the manufacturing process of these FPD, organic EL lighting, and solar cell, for example, there is a step of lifting the glass substrate from the surface plate and a step of heat treatment. When lifting the glass substrate in these steps, The following problems arise.

That is, when the glass substrate is increased in size and thinned, an extremely large deflection occurs when it is lifted, and tensile stress acts on the convex surface due to the deflection, and the concave surface becomes. Compressive stress acts. In that case, the glass substrate has a form in which the front surface and the back surface and the end surfaces existing between the outer peripheral ends of both surfaces are connected via a boundary portion, respectively. The stress concentrates on the part. Therefore, when the glass substrate is bent, a large tensile stress is generated around the boundary between the convex surface or back surface and the end surface connected to the surface. Therefore, if there are minute defects such as scratches, cracks, or foreign objects around the boundary between the front and back surfaces and the end surface of the glass substrate, a large tensile stress is generated near the defect when the glass substrate is bent. At the same time, stress concentration occurs in the defect, and the micro defect expands to break the glass substrate all at once.

The same problem occurs in the above-described heat treatment process of the glass substrate. That is, a glass substrate expands with a rise in temperature and shrinks with a decrease in temperature. However, if an inappropriate temperature distribution occurs in the glass substrate in the heat treatment process, expansion and contraction occur in one glass substrate. Thus, tensile stress and compressive stress are mixed. In that case, if a micro defect exists in the vicinity of the boundary between the front and back surfaces of the glass substrate and the end surface and a tensile stress is generated in the boundary, stress concentration occurs in the micro defect, leading to breakage of the glass substrate. .

By the way, this kind of glass substrate is made to have a desired size by dividing. As a dividing method, a scribe line is engraved on the surface of the glass substrate with a diamond chip or the like, and tensile stress is applied to the scribe line. So-called splitting, in which a glass substrate is cut by applying a force so as to act, is generally employed. In such a dividing method, innumerable minute defects are generated at the boundary between the front and back surfaces and the end surface of the glass substrate after the division, so that the glass substrate is deformed or heat-treated as described above. The probability of breakage increases.

According to Patent Documents 1 and 2, in order to cope with such a problem, a chamfered surface is formed by subjecting a boundary portion between the front and back surfaces of the glass substrate and the end surface to a chamfered surface, and a chamfered surface after polishing from the end surface. Smoothing out is disclosed. Specifically, according to Patent Document 1, the end surface of the glass substrate is perpendicular to both the front and back surfaces, the surface maximum unevenness of the end surface is 0.05 mm or less, and the surface maximum unevenness of the chamfered surface is 0.007 mm or less. It is described that it is preferable. According to Patent Document 2, the end surface of the glass substrate is curved outwardly from the outer peripheral ends of both the front and back surfaces, the maximum surface unevenness of the end surface is 0.04 mm or less, and the maximum surface unevenness of the chamfered surface Is preferably 0.007 mm or less.

JP-A-9-278466 JP-A-9-278467

However, since the glass substrates disclosed in Patent Documents 1 and 2 are tempered glass, even if a glass substrate that has not been subjected to a tempering process is subjected to a process for forming a chamfered surface as in the same document, the glass substrate. If the glass substrate is bent or has an inappropriate temperature distribution, the glass substrate cannot be reliably prevented from being damaged. That is, it can be said that the chamfered surface described in each document is not a surface property that can be suitably applied to any glass substrate including the glass substrates used for the above-described applications.

In addition, the surface properties of the chamfered surface of the glass substrate described in each document are defined by using the maximum surface unevenness as a parameter, and the surface properties based on such a rule ensure that the glass substrate is not damaged as described above. Cannot be stopped. In other words, it is not optimal to use the maximum surface roughness as a parameter, so even if the surface properties of the chamfered surface satisfy the provisions described in each of the documents, the substrate may be bent or have an inappropriate temperature distribution. Therefore, the glass substrate cannot be dealt with accurately due to the damage of the glass substrate.

Furthermore, if the surface properties of the chamfered surface specified in the same document, glass particles, etc. generated during the polishing of the end surface and adhering to the surface of the glass substrate are likely to stay on the chamfered surface in the cleaning process. May also be invited. Due to this, in the drying process, glass particles and the like are attached to the surface of the glass substrate, which causes a fatal defect that the quality of the glass substrate is deteriorated.

In addition, the above-mentioned problems are caused by chamfering by polishing at the boundary portion of a glass substrate divided by using a laser such as laser cleaving other than the above-described splitting of the glass substrate. In the case of formation, it can occur in the same manner.

In spite of the unavoidable possibility of the above problems, the actual situation is that no optimum means has been found in the past as a specific means for appropriately defining the surface properties. It is.

In view of the above circumstances, the present invention is made by optimizing the surface properties of the boundary surface (chamfered surface) extending from the front surface and the back surface of the glass substrate to the glass substrate, regardless of whether the strengthening treatment is performed or not. It is a technical problem to reliably prevent the occurrence of breakage due to the bending of the glass and the inappropriate temperature distribution, and to solve the problem of glass particles.

A first invention created to solve the above technical problem is a glass substrate having a front surface and a back surface, and end surfaces existing between outer peripheral ends of the both surfaces, and at least one surface of the front surface and the back surface. and said end face and a chamfered surface is formed at the boundary portion between the ten point average roughness Rz ₂ of the chamfered surface is less than ten-point average roughness Rz ₁ of the end face, and, crude chamfered surface An average length RSm ₂ of the roughness curve element is characterized by being larger than an average length RSm ₁ of the roughness curve element of the end face. The surface roughness is measured using Surfcom 590A manufactured by Tokyo Seimitsu Co., Ltd. (hereinafter the same). Here, the ten-point average roughness Rzjis (Rz ₁ , Rz ₂ ) and the average length RSm (RSm ₁ , RSm ₂ ) of the roughness curve elements conform to JIS B0601: 2001 (the same applies hereinafter). ). Furthermore, the “chamfered surface” means the surface of the chamfered portion obtained by chamfering the boundary portion (hereinafter the same).

According to such a configuration, the ten-point average roughness of the chamfered surface formed at the boundary portion between at least one of the front and back surfaces of the glass substrate and the end surface is smaller than the ten-point average roughness of the end surface. Not only that, the average length of the roughness curve element of the chamfered surface is made larger than the average length of the roughness curve element of the end face. Thus, by defining the relationship between the surface properties of the chamfered surface and the surface properties of the chamfered surface using the ten-point average roughness Rzjis and the average length RSm of the roughness curve elements as parameters, the boundary portion is missing as a starting point. Or cracks occur and the glass substrate is lost or damaged, glass pieces or glass particles are peeled and removed from the boundary, glass particles stay in the boundary in the cleaning process, and drying process. Problems such as glass particles adhering to the surface of the glass substrate and degrading the quality are effectively avoided. And the glass substrate which concerns on this 1st invention can acquire the above advantages, even if it does not perform the reinforcement | strengthening process (thermal reinforcement | strengthening process).

In the first invention, the chamfered surface has a ten-point average roughness Rz ₂ and an end surface has a ten-point average roughness Rz ₁ that satisfies Rz ₂ ≦ 1.5 μm and 1.5 ≦ Rz ₁ / Rz. It is preferable to satisfy the relationship of ₂ ≦ 10.0.

Thus, by the ten-point average roughness Rz ₂ of the chamfered surface formed on the boundary portion of the a 1.5μm or less, breakage of the glass substrate as a starting point the boundary is more reliably While being suppressed, the breaking strength around the end face is increased, and problems such as generation and retention of glass particles at the boundary are further effectively avoided. If the value (Rz ₁ / Rz ₂ ) obtained by dividing the ten-point average roughness Rz ₁ of the end face by the ten-point average roughness of the chamfered face is less than 1.5, The effect of increasing the breaking strength is reduced. On the other hand, if Rz ₁ / Rz ₂ exceeds 10.0, the difference in roughness between the chamfered surface and the end surface increases, and damage due to new stress concentration may be induced at the boundary between both surfaces. . Accordingly, Rz ₁ / Rz ₂ is preferably within the above numerical range.

Further, in the first invention, the average length RSm ₂ of the roughness curve element of the particular polished surface, it is preferable to satisfy the relation of RSm ₂ ≧ 100μm.

In this way, problems such as breakage of the glass substrate starting from the boundary and generation and retention of glass particles at the boundary can be more effectively avoided. In particular, since RSm ₂ ≧ 100 μm increases the crevice unevenness interval (cycle) of the chamfered surface and suppresses the surface area, the problem of glass particles adhering to the effective surface (surface) is effectively avoided. Is done. In this case, the ratio of the average lengths of the roughness curve elements, that is, RSm ₁ / RSm ₂ is preferably 0.1 or more and 0.7 or less. That is, when RSm ₁ / RSm ₂ is less than 0.1, the difference in the waviness unevenness between the end face and the chamfered surface becomes large, and the surface properties rapidly change at the boundary between the two. A new breakage origin occurs at the boundary. On the other hand, when RSm ₁ / RSm ₂ exceeds 0.7, the difference between the waviness unevenness between the end face and the chamfered portion becomes small, and as a result, the unevenness is formed by the formation of the chamfered surface. It is not removed efficiently, and the effect of increasing the breaking strength is insufficient. Accordingly, RSm ₁ / RSm ₂ is preferably within the above numerical range.

A second invention created in order to solve the above technical problem is a glass substrate having a front surface and a back surface and end surfaces existing between outer peripheral ends of both surfaces, and at least one surface of the front surface and the back surface. A chamfered surface is formed at a boundary portion between the first and second end surfaces, and a protruding valley depth Rvk at the chamfered surface satisfies a relationship of Rvk ≦ 0.95 μm. Here, the protruding valley depth Rvk conforms to JIS B0671-2: 2002 (hereinafter the same).

According to such a configuration, the surface property of the chamfered surface formed at the boundary portion of the glass substrate is defined using the protruding valley depth Rvk as a parameter, and the Rvk is equal to 0. Since it is a glass substrate having a chamfered surface defined as 95 μm or less, the problem of breakage due to bending of the glass substrate and improper temperature distribution and degradation of quality due to glass particles are suppressed as much as possible. That is, the protruding valley depth Rvk is a value indicating how much the portion deeper than the average unevenness of the surface is, and if this value is large, an abnormally deep valley portion exists. become. If the boundary portion has such an abnormal valley portion, when the tensile stress is generated in the boundary portion due to bending or an inappropriate temperature distribution, the stress concentration is abnormally deep in the valley portion. As a result, breakage is likely to occur, and the glass particles are likely to remain and stay in the abnormally deep valley portion. However, if the projecting trough depth Rvk of the chamfered surface formed at the boundary portion is 0.95 μm or less as described above, there is no abnormally deep trough portion at the boundary portion. The stress concentration is less likely to occur even if acts, and the glass particles are less likely to remain. From such a viewpoint, it is more preferable that the protruding valley depth Rvk of the chamfered surface formed at the boundary portion is 0.20 μm or less. In addition, it is effective that the protruding valley depth Rvk at the boundary portion of the glass substrate is smaller than the protruding valley depth Rvk of the end surface connected to the chamfered surface of the boundary portion. That is, it has been found that when stress is generated inside the glass substrate due to bending of the glass substrate or an inappropriate temperature distribution, these stresses are most likely to occur near the boundary. Therefore, if the protruding valley depth Rvk of the boundary portion is made smaller than the protruding valley depth Rvk of the end face, an abnormally deep valley portion that causes the stress concentration is generated from the boundary portion where stress concentration is likely to occur. It will be reduced. As a result, it is possible to reduce as much as possible the damage caused by the bending of the glass substrate and the inappropriate temperature distribution, and in addition to this, the problem of remaining glass particles is avoided. In addition, even if the protruding valley depth Rvk at the end surface of the glass substrate is smaller than the protruding valley depth Rvk of the chamfered surface of the boundary portion, although it becomes an excessive quality from the viewpoint of surface properties, The problem will not be disturbed. And even in the glass substrate which concerns on this 2nd invention, even if it does not perform the reinforcement | strengthening process (thermal reinforcement | strengthening process) or is performed, the above advantages can be acquired.

A third invention devised to solve the above technical problem is a glass substrate having a front surface and a back surface, and end surfaces existing between outer peripheral ends of both surfaces, and at least one surface of the front surface and the back surface. A chamfered surface is formed at a boundary portion between the surface and the end surface, and the root mean square slope RΔq of the roughness curve on the chamfered surface satisfies the relationship of RΔq ≦ 0.10. Here, the root mean square slope RΔq of the roughness curve conforms to JIS B0601-2001 (the same applies hereinafter).

According to such a configuration, in addition to the fact that the surface property of the chamfered surface formed at the boundary portion of the glass substrate is defined using the root mean square slope RΔq of the roughness curve as a parameter, the RΔq Is a glass substrate having a chamfered surface defined as 0.10 or less, it is possible to suppress as much as possible problems of breakage due to bending of the glass substrate and improper temperature distribution and degradation of quality due to glass particles. Is done. That is, the root mean square slope RΔq of the roughness curve is an average value of the slope of each concave portion and each convex portion of the roughness curve with respect to the normal of the surface. This means that there are many concave portions in which the valley bottom has a sharp shape. If the boundary portion is a chamfered surface having such a property, when a tensile stress is generated in the boundary portion due to bending or an inappropriate temperature distribution, stress concentration occurs in the concave portion where the bottom of the valley forms a sharp shape. As a result, breakage is likely to occur, and the glass particles are liable to remain in the recesses. However, when the root mean square slope RΔq of the roughness curve in the chamfered surface formed at the boundary portion as described above is 0.10 or less, the boundary portion has few concave portions having sharp valley bottoms so as not to cause a problem. For this reason, even if tensile stress acts on the boundary portion, stress concentration is less likely to occur, and the glass particles are less likely to remain. From such a viewpoint, the root mean square slope RΔq of the roughness curve on the chamfered surface formed at the boundary is more preferably 0.05 or less. In addition, it is effective that the root mean square slope RΔq of the roughness curve at the boundary surface of the glass substrate is smaller than the root mean square slope RΔq of the roughness curve of the end surface connected to the boundary surface. That is, it has been found that when stress is generated inside the glass substrate due to bending of the glass substrate or an inappropriate temperature distribution, these stresses are most likely to occur near the boundary. Therefore, if the root mean square slope RΔq of the roughness curve of the boundary portion is made smaller than the root mean square slope RΔq of the end surface roughness curve, it causes stress concentration from the boundary portion where stress concentration is likely to occur. The recessed part with which the valley bottom was made sharp is reduced. As a result, it is possible to reduce as much as possible the damage caused by the bending of the glass substrate and the inappropriate temperature distribution, and in addition to this, the problem of remaining glass particles is avoided. Even if the root mean square slope RΔq of the roughness curve at the end face of the glass substrate is smaller than the root mean square slope RΔq of the roughness curve at the chamfered surface of the boundary, the quality is excessive from the viewpoint of surface properties. There will be no hindrance to breakage or glass particle problems. Even in the glass substrate according to the third aspect of the present invention, the above-described advantages can be obtained even if the strengthening process (thermal strengthening process) is not performed or is performed.

A fourth invention devised to solve the above technical problem is a glass substrate having a front surface and a back surface, and end surfaces existing between the outer peripheral ends of the both surfaces, and at least one surface of the front surface and the back surface. A chamfered surface is formed at a boundary portion between the first and second end surfaces, and the maximum valley depth Rv in the chamfered surface satisfies the relationship of Rv ≦ 2.0 μm. Here, the maximum valley depth Rv conforms to JIS B0601-2001 (the same applies hereinafter).

According to such a configuration, the surface property of the chamfered surface formed at the boundary portion of the glass substrate is defined using the maximum valley depth Rv as a parameter, and the Rv is 2.0 μm. Since the glass substrate has a chamfered surface defined as follows, the problem of breakage due to bending of the glass substrate and an inappropriate temperature distribution and the deterioration of quality caused by glass particles are suppressed as much as possible. That is, in the roughness curve representing the properties of the chamfered surface, there are crests and troughs, but when the troughs are deep, if tensile stress due to bending or heat acts on the chamfered surfaces, the troughs As a result, stress concentration occurs at the bottom of the valley so that the glass substrate is torn, and the tearing of the valley develops due to this, thereby causing the glass substrate to break. However, when the maximum valley depth Rv of the chamfered surface is 2.0 μm or less as described above, the chamfered surface has a valley portion having such a depth that tearing develops due to heat or bending tensile stress. As a result, the glass substrate is not easily damaged, and the glass particles hardly remain in the valleys. From such a viewpoint, it is more preferable that the maximum valley depth Rv of the chamfered surface formed at the boundary portion is 1.5 μm or less. In addition, it is effective that the maximum valley depth Rv on the chamfered surface of the glass substrate is smaller than the maximum valley depth Rv of the end surface connected to the chamfered surface. That is, it has been found that when stress is generated inside the glass substrate due to bending of the glass substrate or an inappropriate temperature distribution, these stresses are most likely to occur near the boundary. Therefore, if the maximum valley depth Rv of the boundary portion (chamfered surface) is made smaller than the maximum valley depth Rv of the end surface, a deep valley portion that causes the stress concentration is generated from the boundary portion where stress concentration easily occurs. It will be reduced or disappeared. As a result, it is possible to reduce as much as possible the damage caused by the bending of the glass substrate and the inappropriate temperature distribution, and in addition to this, the problem of remaining glass particles is avoided. In addition, even if the maximum valley depth Rv at the end face of the glass substrate is smaller than the maximum valley depth Rv at the chamfered surface of the boundary portion, although it becomes excessive quality from the viewpoint of surface properties, it is a problem of breakage and glass particles. There will be no hindrance. Even in the glass substrate according to the fourth invention, the above-described advantages can be obtained even if the strengthening process (thermal strengthening process) is not performed or is performed.

In any of the first to fourth inventions described above, the chamfered surface is preferably formed by a polishing process.

That is, if a chamfered surface is formed at the boundary portion of the glass substrate by performing the same polishing process, the surface properties (Rzjis and RSm, second in the first invention) Rvk in the present invention, RΔq in the third invention, and Rv in the fourth invention) can be made uniform. Therefore, a chamfer having a uniform surface property over the entire length in the longitudinal direction at the boundary portion of a single glass substrate. A surface can be formed. In addition, it is possible to form a chamfered surface having the same surface property at each boundary portion for a plurality of glass substrates, regardless of the difference in glass substrates, and to reduce variation in quality. Become.

Furthermore, it is preferable that the chamfered surface is formed by a polishing process after the end surface is polished.

That is, by first polishing the end surface of the glass substrate, the surface properties of the end surface are appropriately improved (Rzjis is reduced and RSm is increased in the first invention, Rvk is reduced in the second invention, In the third invention, RΔq is reduced, and in the fourth invention, Rv is reduced), and then the surface property of the chamfered surface is made better than the surface property of the end surface by forming a chamfered surface by polishing. It is possible to achieve surface properties that can efficiently solve the problem of glass substrate breakage and particles. Therefore, it is an efficient process from the viewpoint of surface properties.

In the above configuration, the end surface can be formed as a flat surface between the outer peripheral ends of the front surface and the back surface.

In this way, since each boundary portion between both the front and back surfaces and the end surface is in an angular state, from the viewpoint of relaxation of tensile stress, the significance of forming a chamfered surface at the boundary portion is growing. In this case, the end surface of the glass substrate may be subjected to a polishing process, or a glass substrate that has been divided using a laser, such as laser cutting, is subjected to a polishing process. It does not have to be. That is, when the glass substrate is divided by laser cleaving or the like, the surface properties of the end surface of the glass substrate formed as a flat surface are close to the same surface as the front and back surfaces, so the end surface is polished. Without it, it is sufficient to form a chamfered surface by polishing at the boundary.

Also, the end surface can be formed as a curved surface that gradually protrudes outward from the outer peripheral ends of the front and back surfaces to the center portion of the plate thickness.

In this way, the connecting portion between the chamfered surface and the end surface and the connecting portion between the chamfered surface and the front surface (or the back surface) can be connected via a gentle bent portion, so that the periphery of the chamfered surface This is advantageous in reducing the tensile stress or stress concentration generated in the case.

In the case of such an end face shape, in a cross section orthogonal to the longitudinal direction of the end face and orthogonal to the front surface and the back surface, a tangent to the front surface side of the chamfered surface formed at the boundary portion on the front surface side, and the front surface And the angle β formed between the tangent to the back surface side of the chamfered surface formed at the boundary portion on the back surface side and the back surface is 10 ° ≦ α ≦ 30 ° and 10 ° ≦ β, respectively. It is preferable that the relationship of ≦ 30 ° is satisfied.

That is, for example, as shown in a plan view in FIG. 7, after polishing only the end surface 3b1 having an arcuate cross section that protrudes outwardly toward the center of the plate thickness, the end surface 3b1 and the front surface (or back surface) 2a1 The boundary portion z1 has an uneven shape, and this boundary portion z1 originally exists at the position indicated by the straight line zx, but is actually biased toward the center side of the front surface (or back surface) 2a1. Will exist. Such a phenomenon is caused by the fact that the abrasive grains of the grindstone bite into the front surface (or back surface) 2a1 side rather than the straight line zx that should be the original boundary when the end surface 3b1 of the glass substrate 11 is polished. This is caused by peeling off the front surface (or back surface) 2a1 side portion. However, as shown in a longitudinal section in FIG. 8, the grindstone 6b1 of the grindstone is about 45 ° in the vicinity of the straight line zx that should essentially be the boundary between the front surface (or back surface) 2a1 of the glass substrate 11 and the end surface 3b1. If the contact is made with the inclination, the grinding surface 6b1 of the grindstone is not in contact with the actual boundary portion z1. Therefore, the grindstone cannot polish the uneven boundary portion z1 or can only polish a part of the boundary portion z1, and as a result, the uneven boundary portion z is completely polished. Therefore, a situation occurs in which a chamfered surface made of a specific polished surface cannot be formed at this boundary portion. Therefore, the angles α and β are preferably set to 45 ° or less. However, when the angles α and β are smaller than 10 °, the polishing region on the end surface side when the chamfered surface is formed by polishing becomes narrow. In order to avoid glass chipping or chipping or cracks remaining at the boundary between the end surface and the front surface (or the back surface), the polishing region is on the front surface side (or the back surface side). ) Is required to be widened, resulting in an unfavorable form as a boundary. On the other hand, when the angles α and β exceed 30 °, the chamfered surface cannot be formed unless the polishing region on the end surface side is excessively wide when the chamfered surface is formed by polishing. Invite the deterioration. Therefore, if the angles α and β are within the above numerical range, these problems do not occur. From such a viewpoint, more preferably, the lower limits of the angles α and β are 15 ° and the upper limit is 20 °.

In the above configuration, the plate thickness T preferably satisfies the relationship of 0.05 mm ≦ T ≦ 1.1 mm.

That is, when the thickness T of the glass substrate exceeds 1.1 mm, the influence of the thickness T of the glass substrate on the strength of the glass substrate increases, and the stress due to the bending or the inappropriate temperature distribution that leads to the breakage of the glass substrate described above. There is a possibility that the effects unique to the present invention (first to fourth inventions) for combating the above cannot be fully exhibited. On the other hand, when the plate thickness T of the glass substrate is less than 0.05 mm, it may be difficult to perform an appropriate polishing process on the boundary portion between both the front surface and the back surface. Therefore, if the thickness T of the glass substrate is within the above numerical range, such a problem can be avoided. From these viewpoints, more preferably, the lower limit value of the plate thickness T of the glass substrate is 0.1 mm, and the upper limit value is 0.7 mm.

Further, it is preferable that the plate thickness T and the width W in the direction perpendicular to the longitudinal direction of the chamfered surface satisfy the relationship of 0.07 ≦ W / T ≦ 0.30.

That is, when W / T is less than 0.07, the formation area of the chamfered surface is insufficient, and the effect of increasing the end face strength due to the presence of the chamfered surface is reduced. On the other hand, when W / T exceeds 0.30, the time required for forming the chamfered surface is prolonged, and the productivity is lowered. Therefore, if W / T is within the above numerical range, such a problem can be avoided. From these viewpoints, it is more preferable to satisfy the relationship of 0.10 ≦ W / T ≦ 0.20.

In addition, it is preferable that the chamfered surface of the glass substrate having the above configuration is formed over the entire length of the side. However, for a glass substrate having a thin plate thickness, it is difficult to form the chamfered surface by polishing. Considering this, the vicinity of the corner portion in plan view may be excluded from the chamfered surface forming portion.

On the other hand, an invention of a method created to solve the above technical problem is a method of manufacturing a glass substrate formed with the above-mentioned chamfered surface, and a rotating shaft as a polishing tool for polishing the chamfered surface. And using a rotary polishing tool having a polishing surface orthogonal to the surface, and forming the roughness of the outer peripheral portion of the polishing surface to be smaller than the roughness of the inner peripheral portion, and at least one of the front and back surfaces of the glass substrate; By rotating the rotary polishing tool around the rotation axis while moving relatively linearly in the longitudinal direction with respect to the boundary portion between the end surface after the polishing process, the outer peripheral portion and the inner peripheral portion of the polishing surface The chamfered surface is formed by both of the parts.

According to such a method, the polishing surface (abrasive surface) of the rotary polishing tool is orthogonal to the rotation axis, and the roughness of the outer peripheral portion of the polishing surface is smaller than the roughness of the inner peripheral portion. When the rotary polishing tool is rotated about the rotation axis while linearly moving in the longitudinal direction with respect to the boundary portion of the glass substrate, the roughness of the polishing surface is first given. With the small outer peripheral portion, the boundary portion is finely cut (fine polishing) to obtain a so-called “run-in” effect. Thereby, in the initial stage of chamfered surface formation with respect to the boundary portion of the glass substrate, unreasonable stress concentration is suppressed, and occurrence of chipping (initial chipping) or cracks due to flapping of the glass substrate is suppressed, A chamfered surface corresponding to the initial stage is formed at the boundary portion. As the next stage, the rotary polishing tool moves relatively linearly, so that the inner peripheral part having a large roughness on the polishing surface comes into contact with the chamfered surface corresponding to the initial stage described above, and the relative rough polishing is performed. Is called. Since this relative rough polishing increases the speed of polishing, the time for forming a chamfered surface is shortened, and at the start of the relative rough polishing, the boundary portion is finely polished to perform the above-described “run-in”. Therefore, relative rough polishing is smoothly started and progressed without causing the occurrence of cracks, cracks, or the like or the progress thereof. As a final step, the rotary polishing tool further moves relatively linearly, so that the outer peripheral portion having the low roughness on the polishing surface comes into contact with the chamfered surface that has been subjected to relative rough polishing, and finish polishing is performed. Is called. As a result, the occurrence of chipping or cracking at the rear end of the chamfered surface due to the vibration of the rotary polishing tool acting on the chamfered surface from the rear end in the moving direction of the polishing surface is suppressed, and due to relative rough polishing. Thus, the fine grinding powder or glass powder remaining on the chamfered surface is removed. As described above, a series of polishing processes including fine polishing (relative polishing), relative rough polishing, and final polishing are performed along the relative linear movement of a single rotary polishing tool. Since the chamfered surface can be formed in a short time while suppressing the occurrence of chips and cracks, the device is simplified and the quality around the chamfered surface is improved. Once secured, productivity can be significantly improved. It should be noted that either one or both of the rotary polishing tool and the glass substrate may be linearly moved. However, in the case of a large glass substrate having a longitudinal dimension of the boundary portion of the glass substrate of 1000 mm or more, the glass substrate It is advantageous to move the rotating polishing tool in the longitudinal direction of the boundary portion while the tool is fixed on the work table or the like. It is advantageous to move the substrate linearly across the polishing surface. Then, preferably, the surface property of the chamfered surface can be made suitable by bringing the rotary polishing tool into elastic contact with an elastic body such as a spring and press-contacting the boundary portion of the glass substrate. .

Furthermore, an invention of a method created to solve the above technical problem is a method of manufacturing a glass substrate formed by forming a chamfered surface after the above-described end surface polishing treatment, and the method is directed to the end surface of the glass substrate. After performing the rough polishing process, the final polishing process is performed, and then, polishing at a boundary portion between at least one of the front surface and the back surface of the glass substrate and the end surface has a finer particle size than the final polishing process. The chamfered surface is formed by performing a specific polishing process using a tool.

According to such a method, the end face of the glass substrate can be polished efficiently in a short time by rough polishing and finish polishing, for example, in a substantially arc-shaped cross section, and the end face is further polished at a finer grain size as subsequent polishing. The chamfered surface is formed with a finer-grained polishing tool at the boundary portion, instead of being polished to the same shape with a tool. Therefore, the end face strength can be efficiently improved by optimizing the three kinds of surface properties of the end face, the chamfered face, and the front and back faces. And, preferably, by arranging a polishing tool for performing rough polishing processing of the end surface, a polishing tool for performing final polishing processing of the end surface, and a polishing tool for performing specific polishing processing on the same path, Each polishing tool can perform each polishing process while continuously moving relatively linearly, and compared with the case where each process is performed separately, the processing time is greatly reduced and the productivity is improved. It becomes possible to plan. Furthermore, preferably, the surface property of the chamfered surface is made suitable by bringing the polishing tool for performing the specific polishing treatment into pressure contact with the boundary portion of the glass substrate in a state where the polishing tool is elastically supported using an elastic body such as a spring. can do.

As described above, according to the present invention, a chamfered surface is formed at a boundary portion existing between at least one of the front and back surfaces of the glass substrate and the end surface, and the surface properties of the chamfered surface use appropriate parameters. Therefore, even if tensile stress is generated on the chamfered surface due to bending of the glass substrate or an inappropriate temperature distribution, stress that causes cracking or chipping of the glass substrate. Concentration is less likely to occur, the probability of breakage is drastically reduced, and glass particles are less likely to stay and improve the quality of the product.

It is a principal part expansion longitudinal cross-sectional view of the end surface cut | disconnected in the direction orthogonal to the longitudinal direction of the side edge part of the glass substrate which concerns on embodiment of this invention. It is the schematic which shows the glass substrate obtained by cut | disconnecting a glass original plate, and the polishing tool which grind | polishes the end surface part of the glass substrate. It is a longitudinal cross-sectional view which shows the principal part of the glass substrate which performed only the end surface grinding | polishing process. It is a schematic front view which shows the state which is forming the chamfering surface with respect to the glass substrate after an end surface process. It is a schematic plan view which shows the state which is performing the formation process of a chamfering surface with respect to the glass substrate after an end surface process. It is a schematic plan view which shows the principal part of the glass substrate after formation of a chamfered surface. It is a schematic plan view which shows the principal part of the glass substrate which shows the conventional problem. It is a longitudinal cross-sectional view which shows the principal part of the glass substrate which shows the conventional problem.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2a Front surface 2b Back surface 3 End surface 4 Chamfering surface 5 Polishing tool (1st, 2nd polishing tool)
6 Third polishing tool 6a Rotating shaft 6b of third polishing tool Polishing surface (abrasive surface) of third polishing tool
6ba Inner peripheral portion 6bb of the third polishing tool (abrasive surface) Outer peripheral portion A of the third polishing tool's polishing surface (abrasive surface) A tangent line to the surface side of the chamfered surface Boundary portion α angle

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, a glass substrate for FPD typified by LCD is targeted.

FIG. 1 is an enlarged longitudinal sectional view of a main part of the glass substrate 1 according to the present embodiment. In addition, although the figure has shown only the form of the surface 2a side part of the glass substrate 1, the back side part also has comprised the form which becomes substantially symmetrical on both sides of the plate | board thickness direction center line X. As shown in the figure, the glass substrate 1 has a planar surface 2a, an end surface 3 having a convex arcuate cross section, and a planar chamfer formed between the surface 2a and the end surface 3. Surface 4. In other words, in the glass substrate 1, the end surface 3 existing between the outer peripheral ends of the front surface 2 a and the back surface, and the front surface 2 a and the back surface are connected via the chamfered surfaces 4, respectively. In addition, although this glass substrate 1 is not subjected to the tempering process (thermal tempering process or the like), the glass substrate 1 may be subjected to the process.

In this embodiment, the end surface 3 of the glass substrate 1 is a polished surface that has been subjected to a final polishing process after being subjected to a rough polishing process, and the surface 2a is a molded surface, that is, an unpolished surface, and is chamfered. The surface 4 is a specific polished surface that has been subjected to a specific polishing process after the final polishing process of the end surface 3.

Ten-point average roughness Rz ₂ of the chamfered surface 4 of the glass substrate 1 is smaller than the ten-point average roughness Rz ₁ of the end face 3, and an average length RSm ₂ of the roughness curve element of the chamfered surface 4, It is made larger than the average length RSm ₁ of the roughness curve element of the end face 3. The surface 2a, since a mirror surface, the average roughness thereof ten-point is smaller than the ten-point average roughness Rz ₂ of the chamfered surface 4, and the average length of the roughness curve element chamfer It is larger than the average length RSm ₂ of the roughness curve element of 4. In this case, the ten-point average roughness Rz ₂ of the chamfered surface 4 is 1.5 μm or less, and the ratio Rz ₁ / Rz ₂ to the ten-point average roughness Rz ₁ of the polished surface of the end face 3 is 1 .5 or more and 10.0 or less. Further, the average length RSm ₂ of the roughness curve element of the chamfered surface 4 is 100 μm or more, and RSm ₁ / RSm ₂ , which is a ratio with the average length RSm ₁ of the roughness curve element of the end face 3, is 0. .1 or more and 0.7 or less.

The protruding valley depth Rvk of the chamfered surface 4 of the glass substrate 1 is 0.95 or less (preferably 0.20 or less). Since the surface 2 a is a mirror surface, the protruding valley depth Rvk is smaller than the protruding valley depth Rvk of the chamfered surface 4.

Furthermore, the root mean square slope RΔq of the roughness curve of the chamfered surface 4 of the glass substrate 1 is 0.10 or less (preferably 0.05 or less). Since the surface 2a is a mirror surface, the root mean square slope RΔq of the roughness curve thereof is smaller than the root mean square slope RΔq of the roughness curve of the chamfered surface 4.

Further, the maximum valley depth Rv of the chamfered surface 4 of the glass substrate 1 is set to 2.0 μm or less (preferably 1.5 μm or less). Since the surface 2 a is a mirror surface, the maximum valley depth Rv is smaller than the maximum valley depth Rv of the chamfered surface 4.

On the other hand, in the cross section shown in FIG. 1 (the cross section orthogonal to the longitudinal direction of the end surface 3 and orthogonal to the surface 2a and the back surface), the angle α between the tangent line A to the surface 2a side of the chamfered surface 4 and the surface 2a is 10 ° or more and 30 ° or less (18 ° in the present embodiment), and although not shown, the chamfered surface on the back surface also has an angle formed between the tangent to the back surface side and the back surface of 10 ° or more and It is 30 degrees or less (18 degrees in this embodiment).

In this case, the chamfered surface 4 is a periphery of the original boundary portion z that forms a waveform between the surface 2a and the end surface 3 in a state where the polishing process of the end surface 3 has been performed (a periphery of a portion indicated by a broken line in FIG. Is removed by a specific polishing process, and the removed portion has a width W1 from the original boundary z to the end surface 3 side of 70 μm and a width W2 from the original boundary z to the surface 2a side. The region is 30 μm. The angle γ formed between the tangent line B of the original boundary portion z and the surface 2a is 25 ° in the present embodiment.

Further, the glass substrate 1 has a thickness T of 1.1 mm or less and 0.05 mm or more, and is orthogonal to the width W of the chamfered surface 4 (longitudinal direction of the chamfered surface 4 (direction along the side)). W / T, which is the ratio of the thickness 2 in the direction parallel to the front surface 2a and the back surface) and the plate thickness T, is set to be 0.07 or more and 0.30 or less.

The glass substrate 1 having the above-described configuration is manufactured as follows.

Fig. 2 shows scribing at four locations on the surface of the glass glass after molding by the downdraw method, float method, etc., so that areas with roughly rectangular engraving lines are drawn, and the scribe marks are the starting points. As an example, a substantially rectangular glass substrate 1 obtained by folding a glass original plate and a polishing tool 5 for polishing the end surface portion 3a of the glass substrate 1 that has been broken are illustrated. The end surface portion 3a of the glass substrate 1 is first subjected to a rough polishing process using a first polishing tool, and then a final polishing process using a second polishing tool. As shown in FIG. 2, the first polishing tool is a rough polishing rotary grindstone wheel (metal) that is formed by attaching a diamond abrasive grain layer held by a metal bond to an outer peripheral surface having a concave arc shape when viewed from the front. Bond diamond wheel). Then, with the first polishing tool pressed against the end surface portion 3a of the glass substrate 1, the first polishing tool is relatively moved in the longitudinal direction (direction along the side) of the end surface portion 3a of the glass substrate 1. Rough polishing is performed. The second polishing tool is a grinding wheel for finishing polishing (resin bond wheel) having the same shape as the first polishing tool, and fine abrasive grains such as silicon carbide bonded to the outer peripheral surface thereof with polyurethane resin or the like. The second polishing tool is subjected to a final polishing process by moving in the same manner as described above while being pressed against the end surface of the glass substrate 1 subjected to the rough polishing process. As a result, as shown in FIG. The glass substrate 1 has a ten-point average roughness Rzjis of about 1 to 3 μm, a protruding valley depth Rvk of about 1.0 to 1.5, and a root mean square slope RΔq of the roughness curve of about 0.12 to 0. 20. An end surface 3b having a substantially arc-shaped cross section having a maximum valley depth Rv of about 3.0 to 5.0 μm is formed. The formation of the end face 3b of the glass substrate 1 is not limited to the two-stage polishing process as described above, and may be performed by a three-stage or more polishing process.

As described above, when the end surface 3b having a substantially arc-shaped cross section is formed on the glass substrate 1, the boundary portion z between the end surface 3b and the surface 2a, and the boundary portion z between the end surface 3b and the back surface 2b, The chamfered surface 4 is formed by performing a specific polishing process using the third polishing tool 6. As shown in FIG. 4, the third polishing tool 6 has a flat polishing surface (abrasive surface) 6b orthogonal to the rotation shaft 6a. The polishing surface 6b is finer than the second polishing tool. It is made of abrasive grains. The glass substrate 1 is set on the upper surface of the work table (surface plate) 7 with the periphery of the end surface 3b protruding.

Then, while simultaneously pressing and rotating the polishing surface 6b of the two third polishing tools 6 against the boundary z on the front surface 2a side and the boundary z on the back surface 2b side of the glass substrate 1, the third polishing tool The specific polishing process is performed by relatively moving 6 in the longitudinal direction of the boundary portion z of the glass substrate 1. Thereby, a large number of glass chippings and the like remaining at the boundary z of the glass substrate 1 are removed. In this case, the angles formed between the polishing surfaces 6b of the two third polishing tools 6 and the front surface 2a and the back surface 2b of the glass substrate 1 are each set to 10 ° or more and 30 ° or less (18 ° in this embodiment). . Preferably, as shown in FIG. 5, the third polishing tool 6 is a concave portion having a circular central portion, and an inner peripheral side polishing portion 6 ba having a relatively small roughness so as to surround the concave portion, and the roughness Are arranged with a relatively large outer peripheral side polishing portion 6bb, and the boundary portion z of the glass substrate 1 is subjected to a specific polishing treatment by both of the polishing portions 6ba and 6bb. Note that the two third polishing tools 6 are spaced apart from each other in the relative movement direction.

Then, by completing this specific polishing treatment, as shown in FIG. 6 (and FIG. 1), a chamfered surface 4 is obtained by completely removing the boundary portion z between the surface 2a and the end surface 3 of the glass substrate 1. It is formed. By forming the chamfered surface 4, even if a tensile stress caused by the bending of the glass substrate 1 or an inappropriate temperature distribution acts on the chamfered surface 4, no stress concentration occurs on the chamfered surface 4, and the end surface 3 (including the chamfered surface 4) is increased in strength, and the problem of remaining glass particles or glass chipping remaining is also avoided.

In the above embodiment, the present invention is applied to the glass substrate 1 in which the end surface 3 is curved outwardly from the outer peripheral ends of the front surface 2a and the back surface 2b, but the end surface 3 is a flat surface (preferably The present invention can be similarly applied to a glass substrate having a flat surface perpendicular to the front and back surfaces.

Further, in the above embodiment, the present invention is applied to the glass substrate on which the end surface forming the curved surface that gradually protrudes outward from the outer peripheral edge of the front surface and the back surface to the central portion of the plate thickness. The present invention can be similarly applied to a glass substrate in which an end surface forming a flat surface perpendicular to these surfaces is formed between them.

Furthermore, in the said embodiment, although this invention was applied to the glass substrate formed by dividing | segmenting a glass original plate by folding, the glass substrate formed by dividing a glass original plate using a laser or a thermal stress like laser cleaving etc. The present invention can be similarly applied to. In this case, the polishing process is not performed on the end surface forming the flat surface, and the chamfered surface is formed only by the polishing process on the boundary portion.

In the above embodiment, the present invention is applied to a glass substrate for FPD. However, the present invention can also be applied to a glass substrate for organic EL lighting or a solar cell, for example.

In order to confirm the effects of the ten-point average roughness Rzjis and the average length RSm of the roughness curve element on the chamfered surface of the glass substrate illustrated in FIG. 1 as described above, the present inventors have implemented Examples 1a to 1e of the present invention. And Comparative Examples 1a to 1c were compared as follows. In each of these Examples and Comparative Examples, OA-10 manufactured by Nippon Electric Glass Co., Ltd., which was formed by the overflow downdraw method, was used as the glass original plate.

For Examples 1a to 1c and Comparative Examples 1a and 1b of the present invention shown in Table 1 below, as a sample to be used, a glass original plate having a plate thickness of 700 μm is split along a scribe mark so as to have a short side dimension. A glass substrate having a length of 1500 mm and a long side dimension of 1800 mm was obtained. Similarly, for Examples 1d and 1e and Comparative Example 1c, as a sample to be used, a glass original plate having a plate thickness of 500 μm is folded and divided along a scribe mark so that a short side dimension is 550 mm and a long side dimension is Obtained a glass substrate of 670 mm. Then, with respect to the end surface portions of these glass substrates, a polishing process for forming an end surface having a circular arc shape with a convex cross section, and chamfered surfaces at respective boundary portions between the end surface, the front surface, and the back surface after the polishing The specific polishing treatment for forming the film was performed according to the following procedure.

For Examples 1a to 1c and Comparative Examples 1a and 1b of the present invention, first, a rough polishing as a first polishing tool having the form shown in FIG. 2 in a state where a glass substrate is placed on a surface plate and fixed by suction. The outer peripheral surface of the polishing grindstone (abrasive grain # 400) is brought into pressure contact with the end surface portion of the glass substrate and linearly moved at the grinding speed shown in Table 1 to obtain an end surface portion that is a rough surface having a substantially arc-shaped cross section. Formed. Next, similarly, the outer peripheral surface of the rotary grindstone for finishing polishing (abrasive grain # 1000) as the second polishing tool having the form shown in FIG. 2 is brought into pressure contact with the end surface portion after rough polishing of the glass substrate, and Table 1 The end face finished and polished into a substantially circular arc shape was formed by linear movement at the grinding speed shown in FIG. For Examples 1d and 1e of the present invention and Comparative Example 1c, first, the glass substrate is linearly moved at the grinding speed shown in Table 2 while being fixedly arranged at a fixed position as shown in FIG. The outer peripheral surface of the rotating grindstone for rough polishing (abrasive grain # 400) as a polishing tool was brought into pressure contact with the end surface portion of the glass substrate, thereby forming an end surface portion that was a rough surface having a substantially arc-shaped cross section. Next, similarly, while rotating the glass substrate linearly at the grinding speed shown in Table 2, the final polishing rotary grindstone (abrasive grain # 1000) as the second polishing tool having the form shown in FIG. ) Was pressed into contact with the end surface of the glass substrate after rough polishing to form an end surface that was finished and polished into a substantially circular arc cross section.

Thereafter, a specific polishing process was performed with a third polishing tool on each boundary portion between the end surface, the front surface, and the back surface of the glass substrate. As the third polishing tool, there was used a flat diamond polishing plate in which diamond abrasive grains were dispersed in a resin material on a circular base. In addition, the magnitude | size of said abrasive grain and the magnitude | size of the abrasive grain shown to Table 1, 2 are based on JISR6001: 1998.

When performing the specific polishing process, the angle formed by the front and back surfaces of the glass substrate and the tangent line of the chamfered surface (angle α in FIG. 1; the same applies to the back surface side) is 18 ° to 22 ° as appropriate. After adjusting the angle of the 3 polishing tool, a grinding liquid (grinding water) was supplied to the contact surface between the third polishing tool and the glass substrate. Then, while rotating the third polishing tool (polishing plate) at a peripheral speed of 2000 m / min so as to obtain a desired chamfer dimension, it is linearly moved at different grinding speeds as shown in Tables 1 and 2, and near the corner portion. A specific polishing treatment was performed over the entire outer periphery of the glass substrate except for. As described above, the glass substrates of Examples 1a to 1c and Examples 1d and 1e were obtained.

In Examples 1a, 1b, and 1d, the abrasive grains of the third polishing tool are # 3000, and in Examples 1c and 1e, the abrasive grains of the third polishing tool are # 2000, whereas in Comparative Examples 1a to 1c, Without performing the specific polishing process with the third polishing tool, only the rough polishing process with the first polishing tool and the final polishing process with the second polishing tool were performed on the end surface portion of the glass substrate. In all the examples, the moving speed and grinding conditions of the third polishing tool are selected so that the chamfer dimension (chamfer width) is in the range of 60 to 200 μm, and all the end surfaces of the glass substrate as a sample are selected. A substantially flat chamfered surface was formed at the boundary between the front surface and the back surface.

In the above embodiment, a method of forming a chamfered surface at the boundary between the front surface and the back surface of the end surface using the third polishing tool after forming a substantially arc-shaped polished surface on the end surface portion of the glass substrate. However, the first polishing tool, the second polishing tool, and the third polishing tool are installed on the same traveling rail in a state where the glass substrate is sucked and fixed on the surface plate, and simultaneously along the traveling rail. You may make it complete | finish polishing operation | movement continuously by making 3 types of grinding | polishing tools drive | work. In this way, since all polishing processes are completed in a shorter time, the processing efficiency can be remarkably increased, and in the polishing process step of a large-sized glass substrate having a dimension of each side of 1000 mm or more. The handling becomes easy. For glass substrates with small sizes, three types of polishing tools are installed so as to be parallel to the sides of the glass substrate, and each glass substrate is continuously polished while being transported using a transport means such as a transport belt. You may use the method of performing.

On the other hand, for the glass substrates of Examples 1a to 1e and Comparative Examples 1a to 1c, the roughness was measured at a measurement length of 5.0 mm using Surfcom 590A manufactured by Tokyo Seimitsu Co., Ltd., and the glass was measured according to JIS B0601: 2001. The roughness parameters of the ten-point average roughness Rzjis (Rz ₁ , Rz ₂ ) and the average length RSm (RSm ₁ , RSm ₂ ) value of the roughness curve element of the end face and chamfered surface of the substrate were calculated. The ten-point average roughness Rz ₁ , Rz ₂ and the average length RSm ₁ , RSm ₂ of the roughness curve element were subjected to chamfering treatment on 10 glass substrates under the same conditions, and 10 times for each. Measurements were made and evaluated by calculating the average value. The results are shown in Tables 1 and 2 below.

Regarding the strength of the polished glass substrate, the breaking strength was measured by a three-point bending test method using Orientec's Tensilon RTA-250. For the sample of the bending test, a test piece obtained by cutting out the central part of the side of the end face of the glass substrate into a size of 80 × 15 mm is used, and the load is applied with the apex of the end face (the apex of the substantially arc of the cross section) facing upward. The fracture stress (end face strength) σ was measured by applying the load, measuring the load at the time of breakage, and calculating by the equation shown in the following formula 1.

In the above equation (1), P is the breaking load, L is the distance between fulcrums, B is the sample width, and h is the glass thickness.

In Tables 1 and 2 below, the breaking stress of the glass substrate is described, and these are measured for 10 breaking stresses of each Example and each Comparative Example, and the minimum value (the one with the smallest strength) is measured. ). Furthermore, in order to evaluate the adhesion characteristics of the glass particles adhering to or remaining on the surface of the glass substrate, the glass remaining on the surface of the glass substrate after washing and drying each glass substrate of each Example and each Comparative Example The surface particle value per sheet was measured. For the particle value, the number of particles of 1 μm or more was measured using a particle measuring device GI-7200 manufactured by Hitachi High-Technologies Corporation, and the numerical value was converted to the number per square meter. The results are shown in Tables 1 and 2 below. Further, with respect to each glass substrate of each example and each comparative example, the remaining state of the step due to chipping at the boundary portion between the front surface and the back surface of the end face was magnified and observed with a microscope. The results are shown in Tables 1 and 2 below. In this case, in Tables 1 and 2, “○” indicates that no chipping level difference is observed, “Δ” indicates that a small level difference is observed, and “×” indicates a large level level remaining. Indicates what is observed.

Note that an angle α (see FIG. 1) between the surface of the glass substrate and the tangent to the surface side of the chamfering surface adjacent to the surface of the glass substrate during the specific polishing treatment of the chamfered surface, and the back surface of the glass substrate and the chamfering surface adjacent to the surface. Table 3 below shows the actual measurement value of the angle β formed by the tangent to the back surface side and the measured value of the width W of the chamfered surface.

According to Tables 1 and 2 above, it is a matter of course that all of Examples 1a to 1e of the present invention have a small ten-point average roughness at the boundary between the front surface and the back surface of the end surface of the glass substrate and are close to a mirror surface. In other words, a chamfered surface having a sufficient width is formed, and the fracture strength (that is, the end surface strength is 160 MPa) is significantly higher than that of a glass substrate having no chamfered surface as in Comparative Examples 1a to 1c. Super). In addition, on the chamfered surface of each example, it was confirmed that no level difference or minute cracks at the polishing boundary due to chipping were observed, and that good or extremely good results were exhibited in all of the adhesion of glass particles and the like.

Therefore, the glass substrate according to each embodiment of the present invention hardly induces breakage in the post-process, becomes extremely high in strength, and generates very little glass particles due to the end face. Further, even when used in a high-resolution display such as an organic EL, it is possible to effectively suppress a disconnection failure that occurs when a display element or device is formed on a glass substrate.

Further, in the case of each embodiment of the present invention, even if the grinding speed is increased from 100 mm / min to 400 mm / min, the same chamfered surface can be efficiently obtained by appropriately selecting the polishing plate of the polishing tool and setting the grinding conditions. It can be obtained well and the efficiency of the process can be increased.

On the other hand, in each comparative example, not only when the moving speed of the polishing tool is 200 mm / sec or 400 mm / sec but also at a low speed of 100 mm / sec, the minimum fracture strength of the end face is relatively low and the strength is low. There is a risk of causing breakage due to the contact of the conveying means to the end face and the concentration of thermal stress. In any of the comparative examples, since the particle value is relatively high and the chipping level difference at the boundary is large, for example, in the process such as cleaning, drying, transporting, and packing, the glass is higher than the chipping part at the boundary. Particles may peel off and adhere to the glass substrate, causing a disconnection failure when forming a display element or device. Therefore, it was confirmed that the glass substrate according to each example of the present invention was extremely excellent in both the breaking strength and the glass particle as compared with the glass substrate according to these comparative examples.

In order to confirm the effect of the protrusion valley depth Rvk on the chamfered surface of the glass substrate illustrated in FIG. 1 as described above, the inventors of the present invention compare the following Examples 2a to 2d with Comparative Examples. As shown. In each of these examples and comparative examples, OA-10 manufactured by Nippon Electric Glass Co., Ltd. (not subjected to strengthening treatment) formed by the overflow downdraw method was used as a glass original plate.

For Examples 2a to 2d and Comparative Examples of the present invention shown in Table 4 below, as a sample to be used, a glass original plate having a plate thickness of 700 μm is scribed and divided into two pieces, whereby the short side dimension is 1500 mm and A glass substrate having a side dimension of 1800 mm was obtained. As a specific method for dividing the glass original plate, a scribe was made on the surface of the glass original plate with a diamond tip, and a bending moment was applied to the glass original plate so that a tensile stress was generated on the scribe line. As another division method, initial scratches are formed on a part of the glass original plate with a diamond wheel, etc., and this part is irradiated with laser to perform local heating, and then cooled rapidly by blowing a refrigerant. It is also possible to cause the initial crack to progress by cutting the glass original plate. However, in the case of such laser cleaving, the end surface of the glass substrate is a flat surface, and thus has an end surface shape different from those of the glass substrates according to this example and the comparative example.

With respect to the end surface of the glass substrate thus obtained, a cylindrical grindstone whose outer peripheral surface is a cylindrical surface (in this example and the comparative example, the outer peripheral surface is recessed in a substantially arc shape) is rotated. Polishing of the end surface is performed by moving the shaft relatively linearly in the longitudinal direction of the end surface while rotating while pressing in a state where the shaft is arranged in parallel with the normal direction of the surface of the glass substrate. . In this case, as the grindstone for polishing the end surface of the glass substrate, a plurality of types of grindstones having different abrasive grains and binders are prepared. First, the grindstone is rough and the binder is hard, and the grindstone is gradually finer and the binder is softer. Changed to

Next, a substantially flat chamfered surface was formed by polishing at the boundary between the end surface and the front surface (back surface) of the glass substrate that had been subjected to the end surface polishing treatment. In this case, it is essential that the grindstone used for chamfered surface polishing is finer in abrasive grains and softer in binder than the grindstone for polishing the end face described above. In the grindstone for polishing a chamfered surface, the surface pressed against the chamfered surface may be a cylindrical surface or a conical surface, or may be a substantially flat circular end surface or an annular end surface. The surface of the polishing cloth which fixed the grain may be sufficient. These grindstones (or polishing cloths) move linearly relative to the longitudinal direction of the chamfered surface of the glass substrate.

Example 2a shown in Table 4 below will be described specifically. First, the first polishing tool having the form shown in FIG. 2 in a state where the divided glass substrate is placed on the surface plate and fixed by suction. As a rough grinding rotary grindstone (# 400 abrasive grains fixed by metal bond), the outer peripheral surface is linearly moved while being pressed against the end surface portion of the glass substrate, so that the end surface portion is a rough surface having a substantially arc-shaped cross section. Formed. Next, similarly, the outer peripheral surface of the final polishing rotary grindstone (# 1000 abrasive grains fixed by resin bond) as the second polishing tool having the form shown in FIG. 2 is used as the end surface portion after rough polishing of the glass substrate. An end face that was finished and polished into a substantially arc shape in cross section was formed by linearly moving while pressing. Thereafter, a specific polishing process was performed with a third polishing tool on each boundary portion between the end surface, the front surface, and the back surface of the glass substrate. As the third polishing tool, a flat diamond polishing plate obtained by dispersing diamond abrasive grains (# 3000 abrasive grains) in a resin material on a circular base was used. When performing the specific polishing process, the angle formed by the front and back surfaces of the glass substrate and the tangent line of the chamfered surface (angle α in FIG. 1; the same applies to the back surface side) is 18 ° to 22 ° as appropriate. After adjusting the angle of the 3 polishing tool, a grinding liquid (grinding water) was supplied to the contact surface between the third polishing tool and the glass substrate. Then, while rotating the third polishing tool (polishing plate) at a peripheral speed of 2000 m / min so as to obtain a desired chamfered surface width dimension, it extends over the entire outer periphery excluding the vicinity of the corner portion in plan view of the glass substrate. Specific polishing treatment was performed. As described above, a glass substrate of Example 2a was obtained. In addition, the size of the above-mentioned abrasive grains conforms to JIS R6001: 1998. In this case, about Example 2b, 2c, 2d and a comparative example, the abrasive grain of the 1st, 2nd, 3rd polishing tool is different from Example 2a, respectively.

The protrusion valley depth Rvk of the chamfered surface of the glass substrate and the protrusion valley depth Rvk of the end face shown in Table 4 below are measured over a measurement length of 5.0 mm using a surfcom 590A manufactured by Tokyo Seimitsu Co., Ltd. The measurement was performed, and the value of each Rvk was calculated according to JIS B0601: 2001. Each of these two types of protruding valley depth Rvk was evaluated by measuring the chamfered surface on 10 glass substrates under the same conditions for each of the 10 glass substrates, measuring them 10 times, and calculating an average value thereof. did. At the same time, the maximum cross-sectional height Pt of the end surface of the glass substrate and the maximum cross-sectional height Pt of the chamfered surface were determined. In addition, the strength of the end face of the glass substrate was determined as a measure of the ease with which the glass substrate was bent or damaged by thermal stress. For the end face strength of the glass substrate, the fracture strength was measured by a three-point bending test method using Orientsil's Tensilon RTA-250, and this was used as the end face strength. For the sample of the bending test, a test piece obtained by cutting the center part of the end face part of the glass substrate into a size of 80 × 15 mm is used, and a load is applied with the apex of the end face part (vertical arc of the cross section) facing upward. Then, the load at the time of breakage was measured, and the fracture stress (end surface strength) σ was measured by calculating with the above-described equation (1).

Table 4 below shows the protruding valley depth Rvk of the chamfered surface, the end surface strength, the maximum cross-sectional height Pt of the chamfered surface, and the maximum cross-sectional height Pt of the end surface obtained as described above.

In Table 4 above, the maximum cross-sectional height Pt of the end face and the maximum cross-sectional height Pt of the chamfered surface correspond to the maximum height Rmax in JIS B0601: 1982. It can be considered that it corresponds to unevenness. The maximum height Pt of the chamfered surface of the glass substrate of the comparative example is 5.57 μm and 7 μm (0.007 mm) or less, and the maximum height Pt of the end surface is 7.44 μm. Since it is 40 μm (0.04 mm) or less, the conditions of the numerical ranges described in Patent Documents 1 and 2 are satisfied. However, the present inventors have confirmed that the glass substrate according to this comparative example is frequently damaged in the manufacturing process of FPD, organic EL, solar cell and the like. This means that the glass substrate according to the comparative example has insufficient end face strength. Considering this, it can be understood that the end face strength needs to be 160 MPa. And, in Examples 2a to 2d of the present invention, the end face strength exceeds 160 MPa because the protruding valley depth Rvk of the chamfered surface is 0.95 or less, and the end face strength is sufficient. I can grasp. Therefore, defining the protrusion valley depth Rvk of the chamfered surface of the glass substrate to be 0.95 or less suppresses the generation of tensile stress due to the bending of the glass substrate and the inappropriate temperature distribution, thereby enabling stress concentration. It can be confirmed that there is a great significance in reducing the amount of damage and preventing breakage of the glass substrate.

In addition, since the glass substrate divided by laser cutting the glass original plate is close to a mirror surface as in the case of the front and back surfaces, the surface property of the flat surface of the glass substrate is similar to the above on the boundary portion of the glass substrate. Even when a chamfered surface is formed, if the projecting valley depth Rvk of the chamfered surface is 0.95 or less, a result equal to or better than the good results shown in Table 4 above can be obtained. I can guess.

In order to confirm the effect on the root mean square slope RΔq of the roughness curve on the chamfered surface of the glass substrate illustrated in FIG. 1 described above, the inventors of the present invention compared the Examples 3a to 3d of the present invention with the comparative example. This was performed as shown below. In each of these examples and comparative examples, OA-10 manufactured by Nippon Electric Glass Co., Ltd. (not subjected to strengthening treatment) formed by the overflow downdraw method was used as a glass original plate.

For Examples 3a to 3d and Comparative Examples of the present invention shown in Table 5 below, as a sample to be used, a short side dimension of 1500 mm and a long length was obtained by putting a scribe into a glass original plate having a plate thickness of 700 μm and splitting it. A glass substrate having a side dimension of 1800 mm was obtained. As a specific method for dividing the glass original plate, a scribe was made on the surface of the glass original plate with a diamond tip, and a bending moment was applied to the glass original plate so that a tensile stress was generated on the scribe line. As another division method, initial scratches are formed on a part of the glass original plate with a diamond wheel, etc., and this part is irradiated with laser to perform local heating, and then cooled rapidly by blowing a refrigerant. It is also possible to cause the initial crack to progress by cutting the glass original plate. However, in the case of such laser cleaving, the end surface of the glass substrate is a flat surface, and thus has an end surface shape different from those of the glass substrates according to the examples and comparative examples.

With respect to the end surface of the glass substrate thus obtained, a cylindrical grindstone whose outer peripheral surface is a cylindrical surface (in this example and the comparative example, the outer peripheral surface is recessed in a substantially arc shape) is rotated. Polishing of the end surface is performed by moving the shaft relatively linearly in the longitudinal direction of the end surface while rotating while pressing in a state where the shaft is arranged in parallel with the normal direction of the surface of the glass substrate. . In this case, as the grindstone for polishing the end surface of the glass substrate, a plurality of types of grindstones having different abrasive grains and binders are prepared. First, the grindstone is rough and the binder is hard, and the grindstone is gradually finer and the binder is softer. Changed to

Next, a substantially flat chamfered surface was formed by polishing at the boundary between the end surface and the front surface (back surface) of the glass substrate that had been subjected to the end surface polishing treatment. In this case, it is essential that the grindstone used for chamfered surface polishing is finer in abrasive grains and softer in binder than the grindstone for polishing the end face described above. In the grindstone for polishing a chamfered surface, the surface pressed against the chamfered surface may be a cylindrical surface or a conical surface, or may be a substantially flat circular end surface or an annular end surface. The surface of the polishing cloth which fixed the grain may be sufficient. These grindstones (or polishing cloths) move linearly relative to the longitudinal direction of the chamfered surface of the glass substrate.

Example 3a shown in Table 5 below will be described in detail. First, the first polishing tool having the form shown in FIG. 2 in a state where the divided glass substrate is placed on a surface plate and fixed by suction. As a rough grinding rotary grindstone (# 400 abrasive grains fixed by metal bond), the outer peripheral surface is linearly moved while being pressed against the end surface portion of the glass substrate, so that the end surface portion is a rough surface having a substantially arc-shaped cross section. Formed. Next, similarly, the outer peripheral surface of the final polishing rotary grindstone (# 1000 abrasive grains fixed by resin bond) as the second polishing tool having the form shown in FIG. 2 is used as the end surface portion after rough polishing of the glass substrate. An end face that was finished and polished into a substantially arc shape in cross section was formed by linearly moving while pressing. Thereafter, a specific polishing process was performed with a third polishing tool on each boundary portion between the end surface, the front surface, and the back surface of the glass substrate. As the third polishing tool, a flat diamond polishing plate obtained by dispersing diamond abrasive grains (# 3000 abrasive grains) in a resin material on a circular base was used. When performing the specific polishing process, the angle formed by the front and back surfaces of the glass substrate and the tangent line of the chamfered surface (angle α in FIG. 1; the same applies to the back surface side) is 18 ° to 22 ° as appropriate. After adjusting the angle of the 3 polishing tool, a grinding liquid (grinding water) was supplied to the contact surface between the third polishing tool and the glass substrate. Then, while rotating the third polishing tool (polishing plate) at a peripheral speed of 2000 m / min so as to obtain a desired chamfered surface width dimension, it extends over the entire outer periphery excluding the vicinity of the corner portion in plan view of the glass substrate. Specific polishing treatment was performed. As described above, a glass substrate of Example 3a was obtained. In addition, the size of the above-mentioned abrasive grains conforms to JIS R6001: 1998. In this case, about Example 3b, 3c, 3d and a comparative example, the abrasive grain of a 1st, 2nd, 3rd polishing tool is different from Example 3a, respectively.

The root mean square slope RΔq of the chamfered surface roughness curve and the root mean square slope RΔq of the end surface roughness curve of the glass substrate shown in Table 5 below were measured using a Surfcom 590A manufactured by Tokyo Seimitsu Co., Ltd. The roughness was measured over 0 mm, and the value of each RΔq was calculated according to JIS BO601: 2001. Each of these two types of root-mean-square slope RΔq was evaluated by measuring a chamfered surface on 10 glass substrates under the same conditions for each of them, measuring them 10 times, and calculating the average value. . At the same time, the maximum cross-sectional height Pt of the end surface of the glass substrate and the maximum cross-sectional height Pt of the chamfered surface were determined. In addition, the strength of the end face of the glass substrate was determined as a measure of the ease with which the glass substrate is bent or damaged by thermal stress. With respect to the end face strength of the glass substrate, the fracture strength was measured by a three-point bending test method using Orientsil's Tensilon RTA-250, and this was used as the end face strength. For the sample of the bending test, a test piece obtained by cutting the center part of the side of the end face of the glass substrate into a size of 80 × 15 mm is used, and a load is applied with the apex of the end face (vertical arc of the cross section) facing upward. Then, the load at the time of breakage was measured, and the fracture stress (end surface strength) σ was measured by calculating with the above-described equation (1).

Table 5 below shows the root mean square slope RΔq of the chamfered surface, the end surface strength, the maximum cross-sectional height Pt of the chamfered surface, and the maximum cross-sectional height Pt of the end surface obtained as described above.

In Table 5 above, the maximum cross-sectional height Pt of the end surface and the maximum cross-sectional height Pt of the chamfered surface are JIS
Since it corresponds to the maximum height Rmax in B0601: 1982, it can be considered that it corresponds to the maximum surface unevenness of Patent Documents 1 and 2 described above. The maximum height Pt of the chamfered surface of the glass substrate of the comparative example is 5.57 μm and 7 μm (0.007 mm) or less, and the maximum height Pt of the end surface is 7.44 μm. Since it is 40 μm (0.04 mm) or less, the conditions of the numerical ranges described in Patent Documents 1 and 2 are satisfied. However, the present inventors have confirmed that the glass substrate according to this comparative example is frequently damaged in the manufacturing process of FPD, organic EL, solar cell and the like. This means that the glass substrate according to the comparative example has insufficient end face strength. Considering this, it can be understood that the end face strength needs to be 160 MPa. In Examples 3a to 3d of the present invention, the root mean square slope RΔq of the chamfered surface is 0.10 or less, so that the end face strength exceeds 160 MPa, and it is understood that the end face strength is sufficient. it can. Therefore, prescribing the root mean square slope RΔq of the chamfered surface of the glass substrate to be 0.10 or less suppresses the generation of tensile stress due to the bending of the glass substrate and the inappropriate temperature distribution, thereby allowing stress concentration as much as possible. It was confirmed that there was a great significance in reducing the glass substrate and preventing breakage of the glass substrate.

In addition, since the glass substrate divided by laser cutting the glass original plate is close to a mirror surface as in the case of the front and back surfaces, the surface property of the flat surface of the glass substrate is similar to the above on the boundary portion of the glass substrate. Even when a chamfered surface is formed, if the root mean square slope RΔq of the chamfered surface is 0.10 or less, it is estimated that a result equal to or better than the good results shown in Table 5 above can be obtained. it can.

In order to confirm the effect of the maximum valley depth Rv on the chamfered surface of the glass substrate illustrated in FIG. 1 as described above, the present inventors show the comparison between Examples 4a to 4d of the present invention and the comparative example. It was done like that. In each of these examples and comparative examples, OA-10 manufactured by Nippon Electric Glass Co., Ltd. (not subjected to strengthening treatment) formed by the overflow downdraw method was used as a glass original plate.

For Examples 4a to 4d and Comparative Examples of the present invention shown in Table 6 below, as a sample to be used, a short side dimension of 1500 mm and a long length was obtained by putting a scribe into a glass original plate having a plate thickness of 700 μm and splitting it. A glass substrate having a side dimension of 1800 mm was obtained. As a specific method for dividing the glass original plate, a scribe was made on the surface of the glass original plate with a diamond tip, and a bending moment was applied to the glass original plate so that a tensile stress was generated on the scribe line. As another division method, initial scratches are formed on a part of the glass original plate with a diamond wheel, etc., and this part is irradiated with laser to perform local heating, and then cooled rapidly by blowing a refrigerant. It is also possible to cause the initial crack to progress by cutting the glass original plate. However, in the case of such laser cleaving, the end surface of the glass substrate is a flat surface, and thus has an end surface shape different from those of the glass substrates according to the examples and comparative examples.

With respect to the end surface of the glass substrate thus obtained, a cylindrical grindstone whose outer peripheral surface is a cylindrical surface (in this example and the comparative example, the outer peripheral surface is recessed in a substantially arc shape) is rotated. Polishing of the end surface is performed by moving the shaft relatively linearly in the longitudinal direction of the end surface while rotating while pressing in a state where the shaft is arranged in parallel with the normal direction of the surface of the glass substrate. . In this case, as the grindstone for polishing the end surface of the glass substrate, a plurality of types of grindstones having different abrasive grains and binders are prepared. First, the grindstone is rough and the binder is hard, and the grindstone is gradually finer and the binder is softer. Changed to

Next, a substantially flat chamfered surface was formed by polishing at the boundary between the end surface and the front surface (back surface) of the glass substrate that had been subjected to the end surface polishing treatment. In this case, it is essential that the grindstone used for chamfered surface polishing is finer in abrasive grains and softer in binder than the grindstone for polishing the end face described above. In the grindstone for polishing a chamfered surface, the surface pressed against the chamfered surface may be a cylindrical surface or a conical surface, or may be a substantially flat circular end surface or an annular end surface. The surface of the polishing cloth which fixed the grain may be sufficient. These grindstones (or polishing cloths) move linearly relative to the longitudinal direction of the chamfered surface of the glass substrate.

Example 4a shown in Table 6 below will be described specifically. First, the first polishing tool having the form shown in FIG. 2 in a state where the divided glass substrate is placed on a surface plate and fixed by suction. As a rough grinding rotary grindstone (# 400 abrasive grains fixed by metal bond), the outer peripheral surface is linearly moved while being pressed against the end surface portion of the glass substrate, so that the end surface portion is a rough surface having a substantially arc-shaped cross section. Formed. Next, similarly, the outer peripheral surface of the final polishing rotary grindstone (# 1000 abrasive grains fixed by resin bond) as the second polishing tool having the form shown in FIG. 2 is used as the end surface portion after rough polishing of the glass substrate. An end face that was finished and polished into a substantially arc shape in cross section was formed by linearly moving while pressing. Thereafter, a specific polishing process was performed with a third polishing tool on each boundary portion between the end surface, the front surface, and the back surface of the glass substrate. As the third polishing tool, a flat diamond polishing plate obtained by dispersing diamond abrasive grains (# 3000 abrasive grains) in a resin material on a circular base was used. When performing the specific polishing process, the angle formed by the front and back surfaces of the glass substrate and the tangent line of the chamfered surface (angle α in FIG. 1; the same applies to the back surface side) is 18 ° to 22 ° as appropriate. After adjusting the angle of the 3 polishing tool, a grinding liquid (grinding water) was supplied to the contact surface between the third polishing tool and the glass substrate. Then, while rotating the third polishing tool (polishing plate) at a peripheral speed of 2000 m / min so as to obtain a desired chamfered surface width dimension, it extends over the entire outer periphery excluding the vicinity of the corner portion in plan view of the glass substrate. Specific polishing treatment was performed. As described above, a glass substrate of Example 4a was obtained. In addition, the size of the above-mentioned abrasive grains conforms to JIS R6001: 1998. In this case, about Example 4b, 4c, 4d and a comparative example, the abrasive grain of the 1st, 2nd, 3rd polishing tool is different from Example 4a, respectively.

The maximum valley depth Rv of the chamfered surface in the glass substrate shown in Table 6 below is measured with a surfcom 590A manufactured by Tokyo Seimitsu Co., Ltd., and the roughness is measured over a measurement length of 5.0 mm, according to JIS B0601: 2001. The value was calculated. This maximum valley depth Rv was evaluated by measuring 10 times of chamfered surfaces on 10 glass substrates under the same conditions and calculating an average value thereof. At the same time, the maximum cross-sectional height Pt of the end surface of the glass substrate and the maximum cross-sectional height Pt of the chamfered surface were determined. In addition, the strength of the end face of the glass substrate was determined as a measure of the ease with which the glass substrate is bent or damaged by thermal stress. With respect to the end face strength of the glass substrate, the fracture strength was measured by a three-point bending test method using Orientsil's Tensilon RTA-250, and this was used as the end face strength. For the sample of the bending test, a test piece obtained by cutting the center part of the side of the end face of the glass substrate into a size of 80 × 15 mm is used, and a load is applied with the apex of the end face (vertical arc of the cross section) facing upward. Then, the load at the time of breakage was measured, and the fracture stress (end surface strength) σ was measured by calculating with the above-described equation (1).

Table 6 below shows the maximum chamfer depth Rv, end face strength σ, maximum cross section height Pt of the chamfered face, and maximum cross section height Pt of the end face obtained as described above.

In Table 6 above, the maximum cross-sectional height Pt of the end surface and the maximum cross-sectional height Pt of the chamfered surface are JIS
Since it corresponds to the maximum height Rmax in B0601: 1982, it can be considered that it corresponds to the maximum surface unevenness of Patent Documents 1 and 2 described above. In the glass substrate of the comparative example, the maximum height Pt of the chamfered surface is 5.57 μm and 7 μm (0.007 mm) or less, and the maximum height Pt of the end surface is 7.44 μm. Since it is 40 μm (0.04 mm) or less, the conditions of the numerical ranges described in Patent Documents 1 and 2 are satisfied. However, the present inventors have confirmed that the glass substrate according to this comparative example is frequently damaged in the manufacturing process of FPD, organic EL, solar cell and the like. This means that the glass substrate according to the comparative example has insufficient end face strength. Considering this, it can be understood that the end face strength needs to be 160 MPa. In Examples 4a to 4d of the present invention, it is understood that the end face strength exceeds 160 MPa because the maximum valley depth Rv of the chamfered surface is 2.0 μm or less, and the end face strength is sufficient. it can. Therefore, defining the maximum valley depth Rv of the chamfered surface of the glass substrate to be 2.0 μm or less suppresses the generation of tensile stress due to the bending of the glass substrate or an inappropriate temperature distribution, thereby allowing stress concentration as much as possible. It was confirmed that there was a great significance in reducing the glass substrate and preventing breakage of the glass substrate.

In addition, since the glass substrate divided by laser cutting the glass original plate is close to a mirror surface as in the case of the front and back surfaces, the surface property of the flat surface of the glass substrate is similar to the above on the boundary portion of the glass substrate. Even when a chamfered surface is formed, if the maximum valley depth Rv of the chamfered surface is 2.0 μm or less, it is estimated that a result equal to or better than the good results shown in Table 6 above can be obtained. it can.

Claims (15)

In a glass substrate having a front surface and a back surface and end surfaces existing between outer peripheral edges of both surfaces, a chamfered surface is formed at a boundary portion between at least one surface of the front surface and the back surface and the end surface. ten-point average roughness Rz ₂ of the surface is smaller than the ten-point average roughness Rz ₁ of the end face, and the average length of roughness curve element of the chamfered surface RSm ₂ is, roughness curve element of the end face glass substrate being larger than the average length RSm ₁ of. The ten-point average roughness Rz _{2 of the} chamfered surface and the ten-point average roughness Rz ₁ of the end surface are Rz ₂ ≦ 1.5 μm and 1.5 ≦ Rz ₁ / Rz ₂ ≦ 10.0 The glass substrate according to claim 1, wherein: The glass substrate according to claim 2, wherein an average length RSm ₂ of the roughness curve element of the chamfered surface satisfies a relationship of RSm ₂ ≧ 100 μm. In a glass substrate having a front surface and a back surface and end surfaces existing between outer peripheral edges of both surfaces, a chamfered surface is formed at a boundary portion between at least one surface of the front surface and the back surface and the end surface. The protruding valley part depth Rvk in the surface satisfies the relationship of Rvk ≦ 0.95 μm. In a glass substrate having a front surface and a back surface and end surfaces existing between outer peripheral edges of both surfaces, a chamfered surface is formed at a boundary portion between at least one surface of the front surface and the back surface and the end surface. A glass substrate characterized in that a root mean square slope RΔq of a roughness curve on a surface satisfies a relationship of RΔq ≦ 0.10. In a glass substrate having a front surface and a back surface and end surfaces existing between outer peripheral edges of both surfaces, a chamfered surface is formed at a boundary portion between at least one surface of the front surface and the back surface and the end surface. The maximum valley depth Rv in the surface satisfies the relationship of Rv ≦ 2.0 μm. The glass substrate according to any one of claims 1 to 6, wherein the chamfered surface is formed by a polishing process. The glass substrate according to claim 7, wherein the chamfered surface is formed by a polishing process after the end surface is polished. The glass substrate according to claim 8, wherein the end surface is formed as a flat surface between outer peripheral ends of the front surface and the back surface. The glass substrate according to claim 8, wherein the end surface is formed as a curved surface that gradually protrudes outward from the outer peripheral edge of the front surface and the back surface to the central portion of the plate thickness. In a cross section orthogonal to the longitudinal direction of the end surface and orthogonal to the front surface and the back surface, an angle α formed by a tangent to the front surface side of the chamfered surface formed at a boundary portion on the front surface side, and the back surface The angle β between the tangent to the back surface side of the chamfered surface formed on the side boundary and the back surface satisfies the relationship of 10 ° ≦ α ≦ 30 ° and 10 ° ≦ β ≦ 30 °, respectively. The glass substrate according to claim 10. The glass substrate according to claim 11, wherein the plate thickness T satisfies a relationship of 0.05 mm ≦ T ≦ 1.1 mm. The glass substrate according to claim 12, wherein the plate thickness T and the width W in the direction orthogonal to the longitudinal direction of the chamfered surface satisfy a relationship of 0.07 ≦ W / T ≦ 0.30. The method for producing a glass substrate according to claim 7, wherein a rotating polishing tool having a polishing surface orthogonal to a rotation axis is used as a polishing tool for polishing the chamfered surface, and an outer peripheral portion of the polishing surface is used. The rotational polishing tool is formed in a longitudinal direction with respect to a boundary portion between at least one of the front surface and the back surface of the glass substrate and the end surface after the polishing treatment, while forming the roughness smaller than the roughness of the inner peripheral portion. A method for producing a glass substrate, wherein the chamfered surface is formed by both an outer peripheral portion and an inner peripheral portion of the polishing surface by rotating about the rotation axis while relatively linearly moving in a direction. The method for producing a glass substrate according to claim 8, wherein the end surface of the glass substrate is subjected to a rough polishing treatment and then subjected to a final polishing treatment, and then, at least one of the front surface and the back surface of the glass substrate. A method for producing a glass substrate, wherein the chamfered surface is formed by subjecting a boundary portion between a surface and the end surface to a specific polishing process using a polishing tool having a finer particle size than the final polishing process. .

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