JP5868577B2 - Glass substrate and manufacturing method thereof - Google Patents

Description

  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. Organic EL is used not only as a display that uses TFTs to flicker the three primary colors as in OLED, but also as a flat light source such as LCD backlights and indoor lighting sources by emitting light only in a single color (for example, white). It's getting on.

  Each of these FPDs and illuminations is 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, the glass substrate is likely to bend, and tensile stress acts on the convex surface due to the deflection, and compressive stress is applied to the concave surface. Act. 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 also acts 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 micro defects such as scratches, cracks, or foreign matter 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 defects 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 step for the glass substrate. That is, the glass substrate expands as the temperature rises and contracts as the temperature decreases, but if an inappropriate temperature distribution occurs in the glass substrate during the heat treatment process, the glass substrate expands and contracts within one glass substrate. As a result, tensile stress and compressive stress are mixed. In that case, if a micro defect exists around the boundary between the front and back surfaces and the end surface of the glass substrate and tensile stress is generated in the boundary, stress concentration occurs in the micro defect, leading to damage to 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 with a diamond chip or the like on the surface of the glass substrate, and the scribe line has a tensile stress. 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 micro 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 performing a polishing process on the boundary between the front and back surfaces and the end surface of the glass substrate, and the chamfered surface after polishing is more polished than the end surface. Smoothing out is disclosed. Specifically, in Patent Document 1, the end surface of the glass substrate is perpendicular to the front and back surfaces, the maximum surface unevenness of the end surface is 0.05 mm or less, and the maximum surface unevenness of the chamfered surface is 0.007 mm. Is preferred. Further, in Patent Document 2, the end face of the glass substrate is curved outward from the outer peripheral ends of 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 It is described that it is preferably 0.007 mm.

Japanese Patent Laid-Open No. 9-278466 Japanese Patent Laid-Open No. 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. It can be said that the occurrence of breakage of the glass substrate cannot be surely avoided when bending or an inappropriate temperature distribution occurs. 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 circumstances described above, the present invention is made by bending the glass substrate regardless of whether or not the strengthening treatment is performed by optimizing the surface properties of the boundary surface connected to the front and back surfaces and the end surface of the glass substrate. In addition, the technical problem is to reliably prevent the occurrence of breakage due to the unjustified temperature distribution and to solve the problem of glass particles.

The present 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 the both surfaces, and between the front surface and the back surface and the end surface. chamfered surface is formed on at least one of the boundary portion, the root-mean-square roughness Rq of the chamfered surface, 0.3 [mu] m Ri der less and the chamfered surface is characterized the polishing surface der Rukoto. Here, the root mean square roughness Rq is based on JIS B0601: 2001 (hereinafter the same). In addition, said "chamfering surface" means the surface of the chamfered part obtained by giving a chamfering process to the said boundary part.

  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 root mean square roughness Rq as a parameter, and this Rq is a measurement curve. Since it is the square root of the average value of the squares of the valleys and valleys of the curve, the high peaks and deep valleys existing on the chamfered surface appear as emphasized numerical values. That is, in the polished surface that has been subjected to multi-stage polishing, the valleys are inevitably emphasized rather than the peaks. In addition to this, since the chamfered surface is defined to have an Rq of 0.3 μm or less, there is a possibility that the glass substrate bends or breaks due to an inappropriate temperature distribution, and the quality deteriorates due to glass particles. Is suppressed. In other words, the roughness curve representing the properties of the chamfered surface has crests and troughs, but when the drop between the crests and troughs is large, tensile stress due to bending or heat causes chamfered surfaces. When acting on, the stress concentration is generated at the bottom of the valley so as to tear the valley, and the tear of the valley develops due to this, thereby causing the glass substrate to break. However, when the root mean square roughness Rq of the chamfered surface is 0.3 μm or less as described above, the chamfered surface has a drop that causes tearing to develop in the valley due to tensile stress due to heat or bending. As a result, the glass substrate is not easily damaged, and the glass particles hardly remain in the valleys. From such a viewpoint, the root mean square roughness Rq of the chamfered surface formed at the boundary is more preferably 0.1 μm or less. In addition, it is effective that the root mean square roughness Rq on the chamfered surface of the glass substrate is smaller than the root mean square roughness Rq 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 likely to occur near the boundary. Therefore, if the root mean square roughness Rq of the boundary portion (chamfered surface) is made smaller than the root mean square roughness Rq of the end surface, the valley portion that causes the stress concentration from the boundary portion where stress concentration easily occurs. 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. In addition, even if the root mean square roughness Rq on the end face of the glass substrate is smaller than the root mean square roughness Rq on the chamfered surface of the boundary portion, although it becomes excessive quality from the viewpoint of surface properties, The problem will not be disturbed. And the glass substrate which concerns on this invention can acquire the above advantages, even if it does not perform the reinforcement | strengthening process (thermal reinforcement | strengthening process) or is performed.

In this case, as described above, the chamfered surface is a polished surface .

Therefore, it becomes that this chamfered surface of the case is thus formed in the polishing process, the boundary of a single glass substrate, a chamfered surface having a root mean square roughness Rq of small numbers over the entire length in the longitudinal direction Can be formed. In addition, even for a plurality of glass substrates, it is possible to form a chamfered surface having an equivalent root mean square roughness Rq at each boundary portion regardless of the difference in glass substrates, thereby reducing variations in quality. It becomes possible. Note that if the chamfered surface is treated in a multi-step manner, the crest portion has a surface property close to a flat surface, so that the root mean square roughness Rq on the chamfered surface can be effectively reduced, and cracks can be generated. This is advantageous in avoiding problems of progress and breakage.

  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 face of the glass substrate, the root mean square roughness Rq of the end face is appropriately reduced, and then the root mean square roughness of the chamfered face is formed by polishing. If Rq is made smaller than the root mean square roughness Rq of the end face, it is possible to achieve a surface property capable of efficiently solving the glass substrate breakage and particle problems. 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, the boundary portion between the front surface and the back surface and the end surface is in an angular state. Therefore, from the viewpoint of relaxation of tensile stress, a chamfered surface having a root mean square roughness Rq of 0.3 μm or less is applied to the boundary portion. The significance of forming increases. 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 cutting or the like, the end surface of the glass substrate formed as a flat surface is close to the same surface as the front and back surfaces, so the end surface is polished. Instead, it is sufficient to form a chamfered surface by polishing at the boundary.

  Further, 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 central 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, an angle formed by a tangent to at least one of the front side and the back side of the chamfered surface and at least one of the front side and the back side is 10 It is preferably at least 30 ° and at most 30 °.

  That is, when the angle is smaller than 10 °, the polishing area on the end face side in the case where the chamfered surface is formed by polishing becomes narrow, and the glass chipping remaining at the boundary portion between the end face and the front and back surfaces is reduced. Alternatively, since removal of chips, cracks and the like becomes insufficient, in order to avoid this, it becomes necessary to widen the polishing region on the front and back surfaces, and the boundary portion is not preferable. On the other hand, if the angle exceeds 30 °, the chamfered surface cannot be formed unless the end surface side polishing region is unreasonably widened when the chamfered surface is formed by polishing. Invite. Therefore, if this angle is within the above numerical range, these problems do not occur. From such a viewpoint, more preferably, the lower limit value of the angle is set to 15 ° and the upper limit value is set to 20 °.

  In the above configuration, the plate thickness T is preferably 1.1 mm or less and 0.05 mm or more.

  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 exists a possibility that the effect peculiar to this invention for countering may not fully be exhibited. On the other hand, if the plate thickness T of the glass substrate is less than 0.05 mm, it may be difficult to perform an appropriate polishing process between the front and back surfaces and the end surfaces. 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.

Here, the present invention is as described above, and the plate thickness T, and width W in a direction perpendicular to the longitudinal direction of the chamfered surface, and satisfy the relationship of 0.07 ≦ W / T ≦ 0.30 Yes .

  That is, when W / T is less than 0.07, the formation area of the chamfered surface becomes 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, the method according to the present invention, which was created to solve the above technical problem, is a method for producing a glass substrate formed with the above-mentioned chamfered surface, and as a polishing tool for polishing the chamfered surface, Using a rotary polishing tool having a polishing surface orthogonal to the rotation axis, and forming the roughness of the outer peripheral portion of the polishing surface smaller than the roughness of the inner peripheral portion, and after polishing the front and back surfaces of the glass substrate The rotating polishing tool rotates about the rotation axis while moving relatively linearly in the longitudinal direction with respect to at least one boundary portion between the outer peripheral surface and the inner peripheral surface 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 specific polishing process for the boundary portion is performed by rotating the rotary polishing tool around the rotation axis while linearly moving relative to the boundary portion of the glass substrate, first, the outer periphery having a small roughness on the polishing surface. By the portion, the boundary portion is finely cut (fine polishing) to obtain a so-called “running” 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, the method according to the present invention, which was created to solve the above technical problem, is a method of manufacturing a glass substrate formed by chamfering after the end face polishing process described above, and is provided on the end face of the glass substrate. After the rough polishing treatment is performed, the finish polishing treatment is performed. After that, at least one boundary portion between the front and back surfaces of the glass substrate and the end surface has a finer particle size than the final polishing treatment. Migaku Ken process using the ingredients (hereinafter, the polishing process is referred to as "specific polishing process.") it is characterized in forming the chamfered surface by performing.

  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. A chamfered surface is formed with a finer-grained polishing tool at at least one of the boundary portions between the end surface, the front surface, and the back surface instead of polishing the same shape with the 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 at least one boundary portion between the front and back surfaces and the end surface of the glass substrate, and the surface property of the chamfered surface is determined by using the root mean square roughness Rq as a parameter. It is specified by using as The root mean square roughness Rq is a value that can be used as an index that emphasizes the extent of the high peaks and the deep valleys. Therefore, the chamfer that defines Rq to be 0.3 μm or less. The glass substrate according to the present invention having a surface has a stress concentration due to a small drop between a crest and a trough even when a tensile stress is generated on the chamfered surface due to bending or an inappropriate temperature distribution. As a result, the occurrence probability of breakage is drastically reduced, and the glass particles are less likely to stay and improve the product quality.

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.

  Embodiments of the present invention will be described below 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 the present 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 a chamfered surface. Reference numeral 4 denotes a specific polished surface that has been subjected to a specific polishing process after the finish polishing of the end face 3. The root mean square roughness Rq of the chamfered surface 4 is 0.3 μm or less (preferably 0.1 μm or less). In addition, since the surface 2a is a mirror surface, the root mean square roughness Rq thereof is smaller than the root mean square roughness Rq of the chamfered surface 4.

  Further, in the cross section shown in FIG. 1 (cross section orthogonal to the longitudinal direction of the end face 3), the angle α formed 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. (In this embodiment, the angle between the tangent to the back surface side and the back surface is 10 ° or more and 30 ° or less (not illustrated). 18 °).

  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 is performed (a periphery of a portion indicated by a broken line in FIG. 1). 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 between the dimension in the direction) 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 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 is formed with an end surface 3b having a substantially arc-shaped cross section having a root mean square roughness Rq of about 0.2 to 2.0 μm. 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 by 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). The Preferably, the third polishing tool 6, as shown in FIG. 5, the central portion is a circular recess, so as to surround the recess, and the inner peripheral-side polishing portion 6ba roughness is relatively not large, coarse degree is relatively is small has the outer peripheral side polishing portion 6bb array, polishing portion 6ba of the both boundary z of the glass substrate 1 is subjected to a specific polishing process by 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. Since this chamfered surface 4 has a root mean square roughness Rq of 0.3 μm or less, even if tensile stress due to bending of the glass substrate 1 or an inappropriate temperature distribution acts on the chamfered surface 4, Since the surface property of the head and the valley is small, the stress concentration is unlikely to occur on the chamfered surface 4, the fracture strength of the end surface 3 (including the chamfered surface 4) is increased, and the glass The problem of remaining 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.

  Moreover, 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.

  Moreover, in the said embodiment, although this invention was applied to the glass substrate for FPD, it is possible to apply this invention similarly to the glass substrate for organic EL illumination or a solar cell, for example.

  In order to confirm the effect of the glass substrate illustrated in FIG. 1, the present inventors made a comparison between Examples 1 and 2 of the present invention and a comparative example as follows. In each of these examples and comparative examples, OA-10 (not subjected to strengthening treatment) manufactured by Nippon Electric Glass Co., Ltd., which was molded by the overflow downdraw method, was used as the glass original plate.

  For Examples 1 and 2 and Comparative Examples 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 scribed and split into pieces, so that the short side dimension is 1500 mm and long. 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 with different abrasive grains and binders are prepared. First, the grindstone is coarse and the binder is hard, and the grindstone is gradually finer and the binder is softer. Changed to

  Next, about the glass substrate which finished the grinding | polishing process of the end surface, the substantially planar chamfering surface was formed in the boundary part of an end surface and the surface (back surface) by grinding | polishing. 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 1 shown in Table 1 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 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 executing 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. The glass substrate of Example 1 was obtained as described above. In addition, the magnitude | size of said abrasive grain is based on JISR6001: 1998. In this case, with respect to Example 2 and the comparative example, the abrasive grains of the first, second, and third polishing tools are different from Example 1, respectively.

  The root-mean-square roughness Rq of the chamfered surface of the glass substrate shown in Table 1 below is measured using a Surfcom 590A manufactured by Tokyo Seimitsu Co., Ltd., over a measurement length of 5.0 mm, according to JIS B0601: 2001. The value was calculated. This root-mean-square roughness Rq was evaluated by measuring 10 times for chamfered surfaces on 10 glass substrates under the same conditions and calculating the average value. At the same time, the maximum cross-sectional height Pt of the chamfered surface of the glass substrate was 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. About the end surface strength of the glass substrate, the fracture strength was measured by a three-point bending test method using Orientec's Tensilon RTA-250, and this was used as the end surface 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 formula shown by the following formula 1.

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

  Table 1 below shows the root mean square roughness Rq of the chamfered surface, the maximum cross-sectional height Pt of the chamfered surface, and the fracture stress (end surface strength) σ obtained as described above.

  In Table 1 above, the maximum cross-sectional height Pt of the chamfered surface corresponds to the maximum height Rmax according to JIS B0601: 1982, and is therefore considered to correspond to the maximum surface irregularities of the aforementioned Patent Documents 1 and 2. Can do. Since the maximum height Pt of the chamfered surface of the glass substrate of the comparative example is 6.94 μm and 7 μm (0.007 mm) or less, the numerical values described in Patent Documents 1 and 2 described above are used. Meet range requirements. 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 1 and 2 of the present invention, the root mean square roughness Rq of the chamfered surface is 0.3 μm or less, so that the end face strength exceeds 160 MPa, and the end face strength is sufficient. I can grasp. Therefore, prescribing the root mean square roughness Rq of the chamfered surface of the glass substrate to 0.3 μm or less suppresses the generation of tensile stress due to the deflection of the glass substrate and the inappropriate temperature distribution, thereby allowing 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 root mean square roughness Rq of the chamfered surface is 0.3 μm or less, a result equal to or better than the good results shown in Table 1 above can be obtained. I can guess.

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 polishing surface (abrasive surface) of the third polishing tool 6bb Outer peripheral portion A of the polishing surface (abrasive surface) of the third polishing tool A tangent line to the surface side of the boundary surface Boundary portion α angle

Claims (8)

In a glass substrate having a front surface and a back surface and end faces existing between outer peripheral edges of both surfaces, a chamfered surface is formed at at least one boundary portion between the front surface and the back surface and the end surface. glass substrate root-mean-square roughness Rq is, 0.3 [mu] m Ri der hereinafter to and chamfered surface and wherein the polishing surface der Rukoto. The glass substrate according to claim 1, wherein the end surface is formed as a flat surface between outer peripheral ends of the front surface and the back surface. 2. The glass substrate according to claim 1, wherein the end surface is formed as a curved surface that gradually protrudes outward from an outer peripheral end of the front surface and the back surface to a central portion of the plate thickness. In a cross section orthogonal to the longitudinal direction of the end face, an angle formed by a tangent to at least one of the front surface side and the back surface side of the chamfered surface and at least one of the front surface and the back surface is 10 ° or more and 30 ° or less. The glass substrate according to claim 3 , wherein the glass substrate is provided. The plate thickness T is 1.1 mm or less and 0.05 mm or more, The glass substrate in any one of Claims 1-4 characterized by the above-mentioned. And the plate thickness T, and width W in a direction perpendicular to the longitudinal direction of the chamfered surface is to any one of claims 1 to 5, characterized in that satisfies the relationship of 0.07 ≦ W / T ≦ 0.30 The glass substrate as described. It is a method of manufacturing the glass substrate of Claim 1 , Comprising: As a grinding | polishing tool which grind | polishes the said chamfering surface, the rotary grinding tool which has a grinding | polishing surface orthogonal to a rotating shaft is used, and the outer peripheral part of the said grinding | polishing surface is used. The rotational polishing tool is formed in the longitudinal direction with respect to at least one boundary portion between the front and back surfaces 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 around the rotation axis while relatively moving linearly. The method for producing a glass substrate according to claim 1 , wherein a rough polishing process is performed on the end surface of the glass substrate, and then a final polishing process is performed. Thereafter, the front and back surfaces of the glass substrate, the end surface, at least one of the boundary portion, a manufacturing method of a glass substrate and forming the chamfered surface by applying a grinding tool Migaku Ken process with having a finer granularity than the final polishing process between.

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