JPH082933A - Chamfering of glass substrate - Google Patents

Abstract

PURPOSE:To enable the chamfering of a number of small-sized glass substrates over the whole circumference of each substrate at the same time by placing glass substrates between upper and lower boards and heating for a prescribed period at a temperature lower than the melting point of the glass. CONSTITUTION:Glass substrates 1 are placed on a flat lower board 2 interposing a definite space between the substrates. An upper board 3 having a flat contacting face is placed on the glass substrates 1 to sandwich the substrates between the boards. The upper and lower boards 2, 3 are preferably made of graphite. As necessary, a spacer having a thickness equal to that of the glass substrate is placed to avoid the application of excessive load on the glass substrate 1 by the upper board 3. The upper and lower boards 2, 3 holding the glass substrates 1 are put into an electric furnace and maintained at a temperature between the yield point and the softening point of the glass in a neutral or reducing atmosphere for a prescribed period (e.g. 60min) to effect the chamfering of the substrate by softening and deforming the edge of the glass substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for chamfering a glass substrate, in which an end face portion of the glass substrate is softened by heating to form a chamfered portion having a smooth roundness. The present invention relates to a glass substrate chamfering method suitable for products requiring dust-free and high accuracy.

[0002]

2. Description of the Related Art Generally, glass has a very sharp cut surface. Normally, glass products used for electro-optical parts are sliced or scribed from flat glass for displays and small pieces of glass such as small filters to have a predetermined size, so that the end face after cutting has an acute angle. Has an edge. However, in the state as it is, it is dangerous in handling, and there is a problem that a crack is generated from a scratch on the end face portion or a new scratch is given to the surface due to a broken glass fragment and the product is deteriorated. For this reason, conventionally, a centering machine has chamfered the end face portions (four corners and eight ridges in the case of a square glass substrate). The problem with the centering machine is that it can process only one piece at a time, so the processing capacity per hour is low, and it is extremely inefficient for small electro-optical parts. Since grinding is performed mechanically with a grindstone, grinding chips are generated and a substrate cleaning process is required.Furthermore, fine cracks that cannot be completely removed with a grinding grindstone or new cracks are formed due to grinding resistance. However, problems such as the occurrence of chipping during the post-process and the middle of transportation, and the adhesion and scratching of the substrate surface due to secondary glass powder generated from it are not completely eliminated. In particular, in recent glass components for electron optics, defects of the order of μm are a problem, so there is a limit in mechanical processing.

As a method for chamfering a glass substrate without using mechanical processing means, Japanese Patent Laid-Open Nos. 54-25 and 57-34049 are known.
Etching method described in Japanese Patent Publication No. 56-1
There is known a method utilizing softening by heating glass as disclosed in Japanese Patent No. 3659 and Japanese Patent Laid-Open No. 2-48423.

[0004]

In the chamfering method by etching described in the above-mentioned JP-A-54-25 and JP-A-57-34049, the grinding scraps and secondary cracks caused by the chamfering are not generated. Although it does not occur, it is difficult to say that it is efficient because it requires cleaning and drying steps of the etching solution. Further, it is difficult to control the concentration of the etching solution, and it is difficult to stably provide products of constant quality.

The method for treating an end surface of a glass plate disclosed in Japanese Patent Publication No. 56-13659 mentioned above is such that electrodes are brought into contact with both ends of the end surface of the glass plate to energize them to increase the temperature of the end surface to a flow temperature range. Is formed in an arc shape, and at the same time, the entire surface of the glass plate is heated to prevent destruction due to a partial temperature difference. According to this method, it is necessary to locally heat and soften only the end face.
It is considered that the processing must be performed for each side as in the embodiment of Japanese Patent No. 3659, and the same operation must be repeated four times to chamfer all four sides, and a circular substrate Not applicable to.

Glass parts for electron optics, for example CCD
In the area sensor cover glass and the like, the glass is placed close to the CCD element, so that flaws, dust, and dirt of the order of μm are defects, and optical distortion is not allowed. Performs precision polishing. In order to prevent chipping of the glass substrate during polishing, it is necessary to chamfer all the end faces. The cover glass for the CCD area sensor is 30 mm square or less, and most of them are 1
Since the size is 0 mm square or less, there are many problems in terms of cost and efficiency in the above method of contacting the electrodes one by one. Further, in the disclosure of Japanese Patent Publication No. 56-13659, the glass plate is placed on a frame, but the upper surface is in contact with the atmosphere, and the glass plate is warped due to the difference in the slow cooling rate after heating. I have a concern.

Next, according to the chamfering method disclosed in the above-mentioned Japanese Patent Laid-Open No. 2-48423, laser light is irradiated to the vicinity of the glass plate including the ridge line portion, the ridge line portion is locally heated and melted, and naturally cooled. It solidifies into an R shape. It is also disclosed that a material having a property of absorbing laser light is applied to the vicinity of the ridge to facilitate heating and softening. In this method, since the glass is naturally heated and then naturally cooled, there is a risk that the glass will be distorted and broken in the subsequent step. In addition, since some glass transmits or reflects most of the laser light, it is necessary to apply a substance having a property of absorbing the laser light, which leads to an increase in the number of steps. JP 2-4842
From the description in Publication No. 3, it is considered that only the ridge is intended to be chamfered, and there is a possibility that an unprocessed part remains in the center of the glass plate end face. If a cutting mark such as a band saw is left on the unprocessed part of the end surface, polishing scraps or abrasives during polishing enter the unevenness, and if these polishing scraps adhere to the polishing surface due to impact during transportation or handling, As described above, some glass components for electron optics cannot be used, which is not preferable.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method capable of chamfering a plurality of relatively small glass substrates simultaneously and over the entire circumference thereof. Also provided is a method capable of smoothing the entire end face without leaving a cutting mark on the end face of the substrate. It is another object of the present invention to provide a method for chamfering a glass substrate without chipping, scratching, or warping, without impairing the outer diameter tolerance.

[0009]

In order to achieve the above object, the present invention utilizes softening of glass by heating and heats a glass substrate under a predetermined condition to soften only the end face portion of the glass substrate. It is what you take.

That is, according to the present invention, the glass substrate is sandwiched between the upper and lower surface plates having flat contact surfaces with the glass substrate, and the glass substrate is heated to a temperature equal to or lower than the softening point of the glass and held for a certain period of time, whereby the end surface portion of the glass substrate is Is a method of softening and deforming. It is preferable that the heating temperature at this time is not less than the yield point of the glass and not more than the softening point of the glass.

More specifically, a glass substrate is placed on a flat lower platen, and an upper platen is placed on the glass substrate and heated and held.
The upper and lower surface plates are preferably made of the same material, and graphite is preferably used as the material.

Further, the present invention is characterized in that a spacer having a thickness equal to that of the glass substrate is arranged between the upper and lower surface plates and is heated and held.

[0013]

By holding the glass substrate at a temperature equal to or lower than the softening point for a certain period of time as in the above structure, the end face portion of the glass substrate is gradually softened, and the surface becomes a smooth R shape due to surface tension. At this time, by sandwiching the glass substrate between the upper and lower surface plates having flat contact surfaces with the glass substrate, the plate surface of the substrate is protected by the surface plate and the end surface portion not in contact with the surface plate is heated. It does not easily interfere with the deformation of the end surface due to softening. In order to soften and deform the glass substrate, a temperature above the sag point is required, and the heating temperature is set above the sag point and below the softening point of the glass. The softening point is the temperature when the viscosity of the glass reaches 10 ^7.6 poise, and the glass is easily softened at this temperature or higher. Therefore, if the heating temperature is higher than the softening point, the chamfering of the end face can be performed in a short time, but on the other hand, rapid softening easily causes the deformation of the substrate, so that the outer diameter variation after the heat treatment is large. Undesirably increases. Therefore, even if the processing time is somewhat longer, the overall efficiency can be increased in consideration of the fact that a large number of substrates can be processed at one time in the present invention and the yield rate is increased. The softening point is preferably not higher than the softening point.

As a specific method, there is a method in which the glass substrate is placed on the flat lower surface plate as described above, the upper surface plate is placed on the glass substrate, and the glass substrate is housed in a heating furnace such as an electric furnace and heated. It's easy. Needless to say, it is preferable to keep the surface plate horizontal. Since the glass substrate is sandwiched between two surface plates, it does not necessarily have to be in a horizontal state, but it is preferably horizontal because the influence of gravity at the time of softening deformation can be made uniform and the glass substrate can be prevented from sliding. .

The surface plate does not fix the glass substrate, but plays a role of preventing warpage of the substrate by appropriate weighting. For this reason, it is necessary for the surface plate to have the same thermal conductivity at the top and bottom, and it is desirable to use the same material for the top and bottom. As a result, the temperature changes (cooling rate) on the upper and lower surfaces of the glass substrate become equal during gradual cooling after the heat treatment, and warpage does not occur.

When a large number of glass substrates are placed between a pair of platens for heating, the platen is made of a material having a high thermal conductivity so that a difference due to the temperature distribution in the heating furnace and the substrate position on the platen is less likely to occur. Is suitable. In addition, graphite is preferable as the material of the surface plate because it can ensure sufficient flatness and is less likely to be welded to the softened glass substrate.

When the upper surface plate is placed on the glass substrate, if the load applied per unit area of the glass is too large, unnecessary deformation occurs such that the softened glass substrate is crushed. Adjust the number and arrangement of glass substrates so that the size of the upper surface plate or the load is distributed so that it will not be applied. Further, as a means for reducing the influence of the load by the upper surface plate and chamfering without impairing the outer diameter tolerance due to the heat treatment, it is possible to dispose a spacer having the same thickness as the glass substrate between the upper and lower surface plates. Conceivable. Use a spacer that is heat-resistant and has little dimensional change due to heat. As a result, the spacer receives the load of the surface plate, prevents an excessive load from being applied to the glass substrate, and has the same thickness as the glass substrate, thereby playing the initial role of the surface plate.

[0018]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. As the glass material, BK-7 which is a general optical glass was used. The yield point of BK-7 is 680 ° C and the softening point is 719 ° C. Glass was previously sliced and lapped into a size of 18.5 × 18.5 × 1.2 mm to obtain a glass substrate 1 for a sample. As shown in FIG. 1, a total of 16 glass substrates 1 are mounted on a lower surface plate 2 of 200 mm square having no undulations or irregularities on the surface of the glass substrate 1 at a constant interval between each glass substrate in 4 × 4 rows. Similar to the lower surface plate 2, an upper surface plate 3 of the same size with no undulations or irregularities is placed on at least the surface in contact with the glass substrate 1.
At this time, the weight of the upper surface plate 3 is adjusted so that the load applied to 1 cm ^{2 of} the glass substrate is 10 g or less in order to avoid unnecessary deformation of the glass substrate 1. The upper and lower surface plates 2 and 3 were both graphite plates.

The glass substrate 1 sandwiched between the upper and lower surface plates 2 and 3 as described above was placed in the electric furnace as it was, and held at a temperature of 680 ° C. for 60 minutes. During this period, the inside of the electric furnace was kept in a reducing atmosphere in order to prevent oxidation of the neutral or graphite. After the heat treatment, the glass substrate 1 is
As shown in the cross section of FIG. 2, the end face had a smooth R shape.

The above operation was repeated to chamfer 100 glass substrates. After allowing to cool, the upper surface plate 2 was removed, and the outer diameter dimension of each glass substrate 1 was measured and compared with the value measured before the heat treatment. Table 1 shows the results. Also,
Except for the softening point, the heating and holding were performed under the same conditions other than the above 7
The outer diameter dimensions before and after the heat treatment were similarly measured and compared for 100 comparative examples which were kept at 30 ° C. for 30 minutes. The results are also shown in Tables 1 and 2.

[0021]

[Table 1]

[0022]

[Table 2]

From the results shown in Tables 1 and 2, in the comparative example heat-treated at a temperature exceeding the softening point, the outer peripheral shape was slightly crushed due to the rapid softening of the end face of the glass substrate and the load of the surface plate. The impression is as follows, and the variation of the outer diameter after the heat treatment is closer to the enlargement side. On the other hand, in the example, the variation before the heat treatment was maintained, and the variation of the outer diameter was also very small.

Thereafter, 100 glass substrates chamfered according to the example and the same quality chamfered by a centering machine using a grinding wheel,
About 100 glass substrates of the same size, the flat plate surface was precision ground, washed, and dried, and then inspected. When chamfered by a centering machine, there are 3 chips that were chipped during polishing.
There were 10 scratches on the polished surface, but no scratches were found on the glass substrate of the example, and only 1 scratch was generated. Even when such post-processing was performed. It was confirmed that the method of the present invention is effective.

Further, the defective substrates are removed from the precision-polished ones, and 100 glass substrates chamfered by the embodiment and 100 glass substrates chamfered by the centering machine are not touched by the glass substrates 1 shown in FIG. As described above, the substrates were separately placed in the transport packages 5 provided with partitions for each substrate, covered with a vinyl chloride lid 6 so as not to move the upper side of the glass substrate, and vacuum packed. The transportation package 5 was vibrated for 60 minutes and then opened to observe the glass substrate. As a result, in the glass substrate chamfered by the centering machine, the substrate end face and the lid 2
Although 12 pieces of glass dust of about 2 to 20 μm, which is thought to be generated from the fine dust or chamfered portion that seems to be generated by the friction with 1, are attached to the flat surface of the glass substrate, However, none of the glass substrates of the examples. Since the glass substrate according to the present embodiment is chamfered by heating and softening, its surface is smooth and dust due to friction with the package is unlikely to be generated, and fine irregularities on the surface such as mechanical grinding and Since no scratches were left, it was confirmed that glass scraps and the like would not be generated by vibration during transportation.

Next, an example using the spacer 4 will be described with reference to FIGS. Similar to the above-mentioned embodiment, the glass substrate 1 is placed on the flat lower plate 2 made of graphite with a certain space between the glass substrates. At this time, a ceramic spacer 4 having the same thickness as the glass substrate 1 is arranged in the gap between the glass substrates 1. As the spacer 4, a rod-shaped object may be arranged so as to sandwich the glass substrate 1 along opposite sides of the surface plate 2 as shown in FIG. 3, or as shown in FIG.
May be dispersedly arranged on the lower surface plate 2 so that the load of the upper surface plate 3 is evenly supported. However, since the glass substrate 1 is softened by heating, the glass substrate 1 and the spacer 4 are arranged so as not to come into contact with each other in order to prevent welding of the spacers. Further, since the rod-shaped spacers 4 may interfere with the air flow between the surface plates, it is necessary to consider the length and arrangement so as not to cause uneven temperature rise of the glass substrate 1. In this respect, the dot-shaped spacers 4 It is preferable to disperse. An upper platen 3 having the same size as the lower platen 2 having a flat surface in contact with at least the glass substrate 1 was placed thereon, and the platen was housed in an electric furnace and held at a temperature of 715 ° C. for 40 minutes in the same manner as in the above example. The glass substrate, its arrangement, and the platen were subjected to the same conditions as in the above-mentioned examples.

By raising the heating temperature as compared with the above-mentioned embodiment, the softening of the glass occurs earlier, and the heating and holding time can be chamfered on the end face 11 of the glass substrate in a shorter time than in the above-mentioned embodiment. Further, as a comparative example, heat treatment was performed under the same conditions without placing the spacers 4, and the outer diameter dimension before and after the heat treatment was measured and compared for each. The results are shown in Tables 3 and 4.

[0028]

[Table 3]

[0029]

[Table 4]

After the heat treatment, the glass substrate 1 has an R shape with smooth end faces, regardless of the presence or absence of the spacer 4, as in the above embodiment. However, as can be seen from the results in Table 2, although the heating temperature and the holding time are the same,
The one that was heat-treated using the spacer had a smaller variation in outer diameter, and was excellent in accuracy.

In this embodiment, a ceramic material is used as the spacer, but graphite, glass, metal, stone material or the like may be used as long as it has sufficient heat resistance at the heating temperature, and is preferably chamfered. It is ideal to use a glass substrate whose coefficient of thermal expansion does not differ greatly from that of the glass substrate.

In each of the above examples, a square plate-shaped surface plate was used. However, if the size of the surface plate is increased or the number of glass substrates processed at one time is increased, a material excellent in thermal conductivity is obtained. Even when used as a surface plate, the glass substrate placed on the center part of the surface plate and the glass substrate on the outer peripheral side heat up faster on the outer peripheral side when placed in a heating furnace. It may be changed, which may affect the outer diameter tolerance and the like. In such a case, a method in which a ventilation hole is provided in the center side of the surface plate that does not correspond to the contact surface with the glass substrate, or a strip-shaped plate on which one or two rows of glass substrates can be placed or covered is used as the surface plate. The temperature difference between the central part and the outer peripheral side of the surface plate is eliminated by a method, or by combining these strip-shaped plates and connecting them with a gap between them to use as one surface plate. You can However, whichever method is used, the flatness of the surface plate must be maintained, and the upper and lower surface plate surfaces to be combined must be parallel to each other.

As the material of the surface plate, ceramics such as SiC and BN can be used in addition to graphite. When ceramics is used, it may be welded to softened glass, so it is advisable to apply a release agent to the contact surface with the glass substrate in advance.

Further, as described above, when the glass substrate placed on the center of the surface plate and the glass substrate on the outer peripheral side are heated in the outer peripheral side faster when they are put into the heating furnace, some of them are heated. It is conceivable that if the glass substrate softens very quickly, the load of the upper platen will be applied there and the outer diameter tolerance will be impaired.
Therefore, in such a case, by disposing the spacers in a distributed manner, it is possible to prevent the load of the surface plate from being unbalanced, and it is possible to perform uniform processing regardless of the position on the surface plate. Not only the arrangements shown in FIGS. 3 to 5, it is effective to arrange the spacers preferentially at a place where the temperature rises quickly. This makes it possible to improve the processing speed by performing heat treatment at a temperature close to the softening point without deteriorating the processing quality. Further, in order to adjust the load of the upper surface plate applied to the glass substrate to an appropriate value, the number and area of the spacers can be adjusted according to the number of glass substrates to be processed and the characteristics of the substrate glass.

Although the glass substrate having a rectangular shape has been described in the above embodiments, the method of the present invention uniformly heats and softens the glass substrate from the outside in the heating furnace, so that the glass substrate has a circular shape or other shapes. However, the end face can be chamfered over the entire circumference by a single treatment.

Further, the heat treatment is not limited to the electric furnace and may be any one capable of heating and maintaining the inside of the furnace at a predetermined temperature. The heating furnace may be a batch furnace or a continuous furnace such as a conveyor furnace.

[0037]

As described above, according to the present invention, a simple method in which a glass substrate is sandwiched between surface plates and heated and held at a temperature below the softening point is used to prevent the substrate from being deformed or warped unnecessarily. With the flat plate surface protected, a large number of glass substrates can be chamfered simultaneously and over the entire circumference of each substrate.
The apparatus configuration required for the present invention is only required to have a heating furnace capable of heating and holding at a predetermined temperature and a pair of surface plates having a flat surface, which can be realized extremely easily and at low cost.

By disposing a spacer having a height equal to the thickness of the glass substrate to be processed between the upper and lower surface plates and performing the heat treatment, the load on the surface plate can be made uniform and the processing accuracy can be improved. .

The upper and lower surface plates are made of the same material, and the temperature changes on the front and back surfaces of the glass substrate to be processed are made uniform, so that the substrate is prevented from warping during the cooling process after heating. In addition, by making the surface plate made of graphite, the temperature difference between the central part and the outer peripheral part of the surface plate is reduced, the processing difference due to the arrangement of the glass substrate is eliminated, and welding with glass does not occur, so the operation is smooth. Can be done.

[Brief description of drawings]

FIG. 1 is a perspective view showing an arrangement relationship between a surface plate and a glass substrate according to an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a state of the glass substrate after the heat treatment in FIG.

FIG. 3 is a plan view showing an embodiment using the rod-shaped spacer of the present invention without an upper surface plate.

FIG. 4 is a front view of a state in which an upper surface plate is placed on FIG.

FIG. 5 is a plan view showing an embodiment using the dot spacers of the present invention without an upper surface plate.

FIG. 6 is a cross-sectional view showing a state where a glass substrate is housed in a transportation package.

[Explanation of symbols]

 1 glass substrate 2 upper surface plate 3 lower surface plate 4 spacer 5 transportation package 6 lid

Claims (6)

[Claims] 1. An end face portion of a glass substrate is softened and deformed by sandwiching the glass substrate between upper and lower surface plates having flat contact surfaces with the glass substrate, heating the glass substrate to a temperature below the softening point of the glass and holding the glass substrate for a certain period of time. A method for chamfering a glass substrate, which comprises: 2. The method for chamfering a glass substrate according to claim 1, wherein the glass substrate is heated and held at a temperature not lower than the yield point and not higher than the softening point of the glass. 3. A glass substrate is placed on a flat lower surface plate,
The chamfering method of the glass substrate according to claim 1 or 2, wherein an upper platen is placed thereon and heated and held. 4. The method for chamfering a glass substrate according to claim 1, wherein spacers having the same thickness as the glass substrate are provided between the upper and lower surface plates. 5. The method for chamfering a glass substrate according to claim 1, wherein the upper and lower surface plates are made of the same material. 6. The method for chamfering a glass substrate according to claim 1, wherein the surface plate is made of graphite.