JP4821696B2 - Glass substrate for flat panel display - Google Patents

Description

  The present invention relates to a glass substrate for a flat panel display, and more particularly to the glass substrate for a display having an exhaust hole that allows gas to pass through from the front surface side to the back surface side.

  As is well known, a plasma display (PDP), which is a kind of flat panel display, includes a glass substrate as a front plate on which electrodes that transmit visible light are formed, and a back plate on which electrodes, ribs, and phosphors are formed. The glass substrate is arranged opposite to each other with a space interposed therebetween. A plasma discharge is generated by applying a voltage to the space between the two plates, and the phosphor on the back plate is caused to emit light by the ultraviolet rays generated thereby, thereby displaying an image. In this case, in order to generate plasma discharge, it is necessary to enclose a gas such as Xe or Ar in the space between the front plate and the back plate. In general, an exhaust hole having a diameter of about several millimeters is formed at least in one place.

  A field emission display (FED) as another example of a flat panel display includes a glass substrate as a front plate on which electrodes and phosphors are formed, and a glass substrate as a back plate on which electrodes and an electron source are formed. Are arranged opposite to each other with a space interposed therebetween. Then, by applying a voltage to the space between the two plates, electrons emitted from the electron source collide with the phosphor, thereby causing the phosphor to emit light and displaying an image. Also in this case, since the space between the front plate and the back plate needs to be high vacuum, exhaust holes are formed in the back plate in the same manner as for the PDP.

  When forming electrodes or the like on the above-mentioned glass substrates for PDP and FED, a heat treatment step is performed in which the glass substrate is heated and cooled so as to be baked or dried. If microcracks or microscratches are present in the glass, stress concentration occurs at the site where the microcracks or the like are present due to thermal stress generated during heating or cooling, and the glass substrate may be damaged.

  More specifically, when a glass substrate is subjected to heat treatment or cooling treatment, due to heat conduction from the surface of the glass substrate, a temperature difference occurs in the thickness direction of the glass substrate, and due to the temperature difference. Distortion occurs inside the glass substrate, which causes a tensile stress near the surface of the glass substrate. In that case, if there are micro cracks of a considerable size on the surface of the glass substrate, tensile stress acts to tear it, and stress concentrates on the bottom of the micro cracks, etc. The micro cracks and the like expand to cause damage to the glass substrate.

  Therefore, in the manufacturing process of PDP and FED, when a transparent electrode is formed on a glass substrate or a phosphor is formed, the glass substrate is forced to be damaged due to heat treatment by heating or cooling. . And the reality is that there is a high probability that such breakage of the glass substrate starts from the exhaust hole of the back plate of the glass substrate.

  In order to cope with this type of problem, the following Patent Document 1 discloses that chamfering is performed on an opening edge of an exhaust hole formed in a glass substrate (back plate) for PDP. That is, the countermeasure disclosed in the same document is based on the assumption that the glass substrate breakage starting from the exhaust hole is caused by a minute chip or the like existing at the opening edge of the exhaust hole. The present invention aims to reduce the probability of occurrence of breakage in the heat treatment process of the glass substrate by cutting off the existence site such as chipping at the opening edge of the glass substrate.

JP 2000-31616 A

  By the way, the present inventors tried to adopt a measure for chamfering as described above, but as a result, although the glass substrate was somewhat damaged in the manufacturing process of PDP and FED, it still remains. It was confirmed that the occurrence of breakage starting from the exhaust hole is the actual situation, and the probability of occurrence is extremely high that cannot be ignored.

  In connection with this, the present inventors have found that the damage of the glass substrate starting from the exhaust hole is not mainly caused by the property of the opening edge of the exhaust hole, but inside the exhaust hole other than the opening edge. It was learned that it was largely derived from the surface properties of the peripheral surface. And since the drilling process of the exhaust hole in the glass substrate is usually performed by a drill, there are micro cracks and micro scratches on the inner peripheral surface polished by the exhaust hole drill. . Therefore, as described above, the damage to the glass substrate is based on the fact that stress concentration occurs in the microcracks and microscratches existing in the glass substrate due to the thermal stress in the heat treatment process. Taking into account, it has also been found that micro cracks and micro scratches present on the inner peripheral surface of the exhaust hole cause breakage of the glass substrate starting from the exhaust hole.

  Therefore, by accurately grasping the relationship between the minute cracks existing on the inner peripheral surface of the exhaust hole and the breakage of the glass substrate starting from the exhaust hole, the probability of occurrence of the breakage of the glass substrate is made possible. In order to reduce this, it is necessary to properly evaluate the surface properties of the inner peripheral surface of the exhaust hole after accurate evaluation. Nevertheless, in the past, the actual situation is that no optimum means has been found for specific means for appropriately evaluating the surface properties.

  In view of the above circumstances, the present invention optimizes the surface properties of the inner peripheral surface of the exhaust hole formed on the glass substrate for flat panel displays typified by PDP and FED, and heat-treats It is a technical problem to reduce as much as possible the probability of breakage of a glass substrate starting from an exhaust hole when performing a process.

  In order to reduce the damage of the glass substrate in the heat treatment process as much as possible as a result of intensive efforts, the inventors firstly, as described above, the exhaust holes formed in the glass substrate. It has been found that the surface properties of the inner peripheral surface should be optimized. Furthermore, it has been found that in order to make it concrete, it is sufficient to prevent thermal stress from concentrating on microcracks and microscratches existing on the inner peripheral surface of the exhaust hole formed in the glass substrate. In that case, even if there are micro cracks or micro scratches on the inner peripheral surface of the exhaust hole, some of them cause damage to the glass substrate and others do not. In connection with this, the present inventors, among micro cracks and micro scratches existing on the inner peripheral surface of the exhaust hole, are subjected to a tensile stress due to heat so as to tear them, and a large stress is applied to the bottom of the valley. In the case where there are micro-cracks or the like that cause concentration, the inventors have obtained knowledge that the micro-cracks and the like are unreasonably progressed to cause damage to the glass substrate.

The present invention, which has been devised in order to solve the above technical problems through the above thought process, is a glass substrate for a flat panel display having an exhaust hole through which gas can flow from the front side to the back side. The maximum valley depth Rv of the inner peripheral surface of the exhaust hole is characterized by being 1.5 μm or less , and for further optimization of the surface properties, the maximum peak height Rp is , Ru characterized in that at 1.2μm or less. Here, the above-mentioned “maximum valley depth Rv” and “maximum mountain height Rp ” are both in accordance with JIS B0601: 2001, and have a cutoff value λc = 0.25 mm and a cutoff ratio λc / λs = It is measured under 100 conditions (hereinafter the same). The “inner peripheral surface of the exhaust hole” includes a chamfered portion when the opening edge of the exhaust hole is chamfered.

  According to such a configuration, the maximum valley depth Rv is used as an evaluation setting element for the surface property on the inner peripheral surface of the exhaust hole. As described above, the reason why the maximum valley depth Rv is used as the evaluation setting element for the surface property is that tensile stress due to heat acts so as to tear the micro cracks and micro scratches existing on the inner peripheral surface of the exhaust hole. In this case, since a large stress concentration occurs at the bottom of the valley such as the microcrack, the microcrack or the like undesirably progresses and damages the glass substrate. Therefore, the valley depth of the microcrack or the like is extremely important. It comes from being a factor.

  And if the maximum valley depth Rv of the inner peripheral surface of the exhaust hole is 1.5 μm or less, even if tensile stress due to heat is concentrated on the bottom of the valley such as a microcrack, the microcrack etc. The situation does not progress, and the probability of occurrence of breakage of the glass substrate starting from the exhaust hole in the heat treatment process becomes extremely low. On the other hand, when the maximum valley depth Rv of the inner peripheral surface of the exhaust hole exceeds 1.5 μm, a large tensile stress caused by heat concentrates on the bottom of the valley such as a microcrack, and so on. Will undesirably progress, and the probability of breakage of the glass substrate starting from the exhaust hole will increase. Therefore, by setting the maximum valley depth Rv to 1.5 μm or less, the surface property of the inner peripheral surface of the exhaust hole is suitable to such an extent that breakage of the glass substrate starting from the exhaust hole in the heat treatment step does not become a problem. Can be.

In addition to the above items, the inner peripheral surface of the exhaust hole, further, the maximum peak height Rp is a 1.2μm or less.

  In this way, the properties of the microcracks and the valley bottoms of the micro-scratches existing on the inner peripheral surface of the exhaust hole are optimized as described above, and the properties of those ridges and the maximum peak height Rp. Due to the synergistic effect with the optimization, the inner peripheral surface of the exhaust hole becomes a smooth surface without undue irregularities. In other words, considering both the maximum valley depth Rv and the maximum peak height Rp, an exhaust hole having an inner peripheral surface having a surface property that does not cause damage in the heat treatment step is formed. In addition, the probability of breakage of the glass substrate starting from the exhaust hole in the heat treatment step is more reliably reduced.

  In this case, the exhaust hole preferably has a diameter of 0.5 mm or more and 5 mm or less.

  In this way, it is possible to easily and smoothly advance the operation such as exhaust through the exhaust hole without reducing the mechanical strength of the glass substrate. That is, if the diameter of the exhaust hole exceeds 5 mm, the mechanical strength and thermal strength of the glass substrate itself may be reduced. On the other hand, if the diameter of the exhaust hole is less than 0.5 mm, the amount of gas that can be exhausted from the exhaust hole per unit time is reduced, which may lead to deterioration in the work efficiency of the exhaust work. Therefore, if the diameter of the exhaust hole is in the above numerical range, such a problem is preferably avoided.

Incidentally, the thickness of the glass substrate is preferably set to 3mm or less.

  In other words, by defining the surface properties of the inner peripheral surface of the exhaust hole as described above, the glass substrate is broken while accurately responding to the demand for thinning that has been promoted in recent years for glass substrates for flat panel displays. Can be greatly reduced.

  And if the glass substrate provided with the above structure is used as a glass substrate for a plasma display or a field emission display, the above-mentioned useful advantages can be obtained accurately.

As described above, according to the present invention, the surface properties of the inner peripheral surface of the exhaust hole in the glass substrate for flat panel displays typified by PDP and FED are composed of the maximum valley depth Rv and the maximum peak height Rp. Since it is optimized using the optimum evaluation setting elements, the glass substrate starting from the exhaust hole is damaged in the heat treatment process such as the baking process and the drying process which is indispensable for manufacturing this type of panel. It is possible to accurately reduce the occurrence probability.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a perspective view schematically showing an overall configuration of a glass substrate for a flat panel display according to the present embodiment. As shown in the figure, the glass substrate 1 for the flat panel display (PDP or FED) has a plate thickness of 0.5 mm to 5 mm, and allows gas to penetrate from the front side to the back side. An exhaust hole 2 is formed. The exhaust hole 2 has a diameter of 0.5 mm to 5 mm and is provided in a range of 2 mm to 50 mm from the side of the glass substrate 1. In the illustrated example, the exhaust hole 2 is formed at one location of the corner portion of the glass substrate 1, but the formation site and the number thereof are not limited to this.

And the surface property of the inner peripheral surface of the exhaust hole 2 affects the presence or absence of breakage of the glass substrate 1 starting from the exhaust hole 2 in a heat treatment process such as a baking process or a drying process included in the flat panel display manufacturing process. Therefore, the maximum valley depth Rv is set to 1.5 μm or less, and the maximum peak height Rp is set to 1.2 μm or less. Thus, if the surface property of the inner peripheral surface of the exhaust hole 2 is set, the inner peripheral surface becomes a smooth surface without unduly deep microcracks or microscratches, and the surface property is such that it does not cause damage in the heat treatment process. It becomes.

  The opening edge portion of the exhaust hole 2 may be chamfered, but it may not be chamfered from the viewpoint of simplifying the work. That is, even if chamfering is not performed, there is no practical problem if the inner peripheral surface of the exhaust hole is set to have a surface property within the above numerical range.

  The exhaust hole 2 is formed by drilling a predetermined position of the glass substrate 1 using a drill 3 shown in FIGS. The drill 3 is formed by attaching diamond abrasive grains having a predetermined particle diameter to the outer surface of a cylindrical main body 3a having a hemispherical tip by a metal bond, and a portion 180 ° apart from the cylindrical main body 3a. In addition, a groove 3x having a V-shaped cross section and extending in parallel with the axis is formed.

  Specifically, the drilling operation is performed by placing the drill 3 having the above-described configuration on the upper surface side and the lower surface side of the glass substrate 1 held in a horizontal posture so as to be opposed to each other, and the drill 3 existing on the upper surface side between the glass substrate 1. Exhaust holes 2 penetrating in the thickness direction of the glass substrate 1 are formed by drilling up to a position (position about 4/5 of the plate thickness), and then drilling the glass substrate 1 with a drill 3 existing on the lower surface side. Is done. Furthermore, when drilling, it is important to increase the number of rotations of the drill and to reduce the speed of the drill 3 with respect to the glass substrate 1. Specifically, for example, the rotation speed of the drill 3 is set within a range of 1000 rpm to 50000 rpm, and the traveling speed thereof is set within a range of 0.1 mm / s to 5 mm / s.

  As described above, according to the glass substrate 1 for a flat panel display according to the present embodiment, the surface property of the inner peripheral surface of the exhaust hole 2 has the maximum valley depth Rv (preferably including the maximum peak height Rp). In the heat treatment process such as a baking process and a drying process that are indispensable for manufacturing a flat panel display, the glass substrate 1 is cracked or cracked from the exhaust hole 2 as a starting point. It is possible to accurately reduce the probability of occurrence of damage.

  As Examples 1 to 7 of the present invention, the maximum valley depth Rv of the inner peripheral surface of the through hole (exhaust hole) is 1.5 μm or less and the maximum peak height Rp is in the range of 1.2 μm or less. 110 glass substrates were produced, and 110 glass substrates for PDP in which the maximum valley depth Rv and the maximum mountain height Rp of the inner peripheral surface of the through hole deviated from the above numerical range were produced as comparative examples. Specifically, as shown in Table 1, Example 1 of the present invention has an Rv of 0.9 μm, Rp of 0.6 μm, and Example 2 has an Rv of 0.9 μm on the inner peripheral surface of the through hole. Rp is 0.7 μm, Example 3 has Rv of 1.0 μm, Rp of 0.8 μm, Example 4 has Rv of 1.1 μm, Rp of 0.9 μm, and Example 5 has Rv of 1. 3 μm, Rp is 1.0 μm, Example 6 is Rv is 1.3 μm, Rp is 1.1 μm, Example 7 is Rv is 1.5 μm, Rp is 1.2 μm, and Comparative Example 1 is Rv is 3.0 μm and Rp is 1.5 μm.

  The glass substrates according to Examples 1 to 7 and Comparative Example of the present invention described above were manufactured and measured under the following conditions. That is, 110 glass substrates for PDP having a length of 100 mm, a width of 100 mm, and a thickness of 1.8 mm were prepared for each of the examples and comparative examples, respectively, and a drill shown in FIG. A through hole (exhaust hole) was formed. In this case, the hole forming method using the drill is such that the first drill is inserted from the upper surface side of the glass substrate held in a horizontal posture, drilled to a depth of approximately 1.5 mm, and then the drill is retracted to return the glass substrate. Then, a second drill from the lower surface side was made to enter the same location as the above-mentioned perforated location of the glass substrate to form a through hole. And in this case, the rotational speed of the drill entering from both sides of the glass substrate is the same for all the examples and comparative examples, and the processing time in Table 1 indicates the time required to form the through hole, The average processing time per sheet for each example and comparative example is shown. The exhaust hole has a diameter of 2 mm, and the opening edge is not chamfered.

  Among the glass substrates according to each of the examples and comparative examples in which the through holes are formed in this way, for each of the 10 glass substrates, the inner peripheral surface of the through hole is exposed by cleaving, and the maximum of the inner peripheral surface is obtained. The valley depth Rv and the maximum mountain height Rp were measured with Surfcom 1400 manufactured by Tokyo Seimitsu Co., Ltd., and the average values were calculated. The measurement conditions in this case were cut-off value λc = 0.25 mm, cut-off ratio λc / λs = 100, stylus tip diameter 5 μm, measurement speed 0.03 mm / sec, filter Gaussian, evaluation length thickness It was set to 1.4 mm excluding both ends in the direction. In addition, for each of the remaining 100 glass substrates, a thermal shock test was performed by heating to 160 ° C. in an electric furnace, and then rapidly cooling with 20 ° C. water applied to the through holes. The damage situation was observed. In this case, if the number of broken glass substrates is two or less, it can be determined that the probability of occurrence of breakage is sufficiently reduced as compared to the conventional case, and that the glass substrate can withstand practical use. Furthermore, about the broken glass substrate among the glass substrates on which the thermal shock test was completed, the occurrence position of breakage in the thickness direction (the shorter position from both surfaces of the glass substrate to the breakage starting point) was measured. The results are shown in Table 1.

  According to Table 1, in Examples 1 to 7, the maximum valley depth Rv is 1.5 μm or less and the maximum peak height Rp is 1 on the inner peripheral surface of the through hole (exhaust hole) formed in the glass substrate. .2 μm or less, the inner peripheral surface of the through hole is smoothed, the strength of practical use against thermal stress can be maintained, and the probability of breakage of the glass substrate starting from the through hole is It can be confirmed that the amount is sufficiently reduced as compared with the prior art. Further, when the maximum valley depth Rv is 1.1 μm or less and the maximum peak height Rp is 0.9 μm or less, the glass substrate is not damaged, and thus the surface property of the inner peripheral surface of the through hole is more preferable. It can also be confirmed. On the other hand, in the comparative example, since the maximum valley depth Rv exceeds 1.5 μm and the maximum peak height Rp exceeds 1.2 μm, the inner peripheral surface of the through hole becomes unreasonably rough, resulting from this. Thus, it can be confirmed that there are large irregularities or the like that cause damage to the glass substrate in the heat treatment step, and the number of breakage of the glass substrate reaches a practical level.

  In Table 1, when focusing on the processing time, if the maximum valley depth Rv is less than 1.0 μm and the maximum peak height Rp is less than 0.8 μm, the processing time of the through hole is unduly increased and produced. It can be confirmed that the sex deteriorates. Therefore, from the viewpoint of maintaining good productivity while reducing breakage of the glass substrate, the maximum valley depth Rv of the inner peripheral surface of the through hole is 1.0 μm or more and 1.5 μm or less, and the maximum peak height Rp. Is preferably 0.8 μm or more and 1.2 μm or less, the maximum valley depth Rv is 1.3 μm or more and less than 1.5 μm, and the maximum peak height Rp is 1.0 μm or more and less than 1.2 μm. More preferable.

It is a perspective view which shows typically the glass substrate for flat panel displays which concerns on embodiment of this invention. Fig.2 (a) is a schematic side view of the drill used when forming an exhaust hole in the said glass substrate, FIG.2 (b) is AA sectional drawing of Fig.2 (a).

Explanation of symbols

1 Glass substrate for flat panel display 2 Exhaust hole 3 Drill

Claims (4)

A glass substrate for a flat panel display having an exhaust hole that allows gas to pass through from the front side to the back side,
A glass substrate for a flat panel display, wherein the maximum valley depth Rv of the inner peripheral surface of the exhaust hole is 1.5 μm or less and the maximum peak height Rp is 1.2 μm or less . The glass substrate for a flat panel display according to claim 1, wherein a diameter of the exhaust hole is 0.5 mm or more and 5 mm or less. Said glass substrate is a glass substrate for a flat panel display according to claim 1 or 2, characterized in that it is a plasma display. The glass substrate for a flat panel display according to any one of claims 1 to 3 , wherein the glass substrate is for a field emission display.

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