JP2011043457A - Inspection method of glass substrate end - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To overcome the problem that it is difficult for an inspection method for irradiating a glass substrate end with light and observing the light scattered from a defect to detect a microcrack within a glass substrate, and the problem that a view field to be observed is narrow, and the inspection efficiency is low in a method for observing the light reflected at the glass substrate end through a refractive body and researching the defect at the glass substrate end. <P>SOLUTION: The glass substrate end is irradiated with the light obliquely entering into the glass substrate, totally reflected within the glass substrate and traveling through the glass substrate, and observed from the outside of the glass substrate end. The light 12 enters into the glass substrate 11 through the refractive body 16 placed in the vicinity of the glass substrate end 13 and having a refractive index larger than the glass substrate 11. The light 12 is totally reflected within the glass substrate 11, travels through the glass substrate 11, and reaches the glass substrate end 13. Since an incident position 17 of the light 12 can be installed near the glass substrate end 13, the light 12 reaches the glass substrate end 13 almost without attenuation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for inspecting a glass substrate end, and more particularly to a method for inspecting a microcrack generated in a shallow portion near the surface of a glass substrate end.

  A glass substrate used for a flat panel display is obtained by polishing an end, an edge, or a corner of a glass plate cut into a rectangle from a strip-shaped glass plate manufactured by a float method, an overflow downdraw method, or the like. .

  These glass substrates have fine defects at the edge of the substrate such as edges, corners, and end faces due to contact with positioning jigs or conveyance jigs or fluctuations in polishing conditions during polishing or conveyance. May occur.

  On the other hand, since the glass substrate is subjected to various heat treatments in the manufacturing process of the flat panel display, if the fine defects exist at the edge of the glass substrate, the glass substrate may be damaged in the heat treatment step or the transport step. Become.

  Therefore, a fine defect at the edge of the glass substrate is optically inspected for the glass substrate that has been polished at the edge. Such an optical inspection of a fine defect is generally performed by irradiating light on the edge of the glass substrate and visually observing or optically processing the scattered light from the defect.

  Further, a refractor (prism) having a higher refractive index than that of the glass substrate is placed on the surface of the glass substrate through the immersion liquid, light is introduced into the glass substrate through the refractor, and the light is totally reflected inside the glass substrate. There has been proposed a method for inspecting defects at the glass substrate end by guiding the light to the end of the glass substrate and observing the light reflected at the end of the glass substrate through the same refractor (Patent Document 1). This method is effective when the edge of the glass substrate cannot be observed directly.

  Further, a refractor (prism) having a higher refractive index than that of the glass substrate is placed on the surface of the glass substrate through the immersion liquid, light is introduced into the glass substrate through the refractor, and the light is totally reflected inside the glass substrate. A method for inspecting a glass substrate by guiding and observing scattered light due to defects inside the glass substrate has been proposed (Patent Document 2).

JP 2003-172712 A JP 2003-329602 A

  Defects generated at the edge of the glass substrate often occur on the surface of the edge, but some of them develop into the glass as microcracks. Although such microcracks are fine, they can cause damage to the glass substrate due to slight thermal or mechanical stress. Therefore, it is important to detect such microcracks.

  However, in a general inspection method in which light is irradiated to the edge of the glass substrate from the observer side and the scattered light from the defect is observed visually or by optical image processing, the light is reflected on the surface of the edge of the glass substrate. There is a problem that it is difficult to reach the inside. Moreover, since light reflects on the surface of the glass substrate edge part and obstructs observation, it is difficult to detect the micro crack inside a glass substrate.

  Furthermore, if the surface of the glass substrate end is a ground or polished surface, it will exhibit a ground glass-like surface, causing irregular reflection of light, thereby detecting microcracks inside the glass substrate, It becomes even more difficult.

  In the inspection method described in Patent Document 1, the light incident on the glass substrate through the refractor is reflected at the glass substrate end, and the returned light is observed through the same refractor to thereby detect defects at the glass substrate end. Therefore, there is a problem that the observable field of view is narrow and the inspection efficiency is low.

  The inspection method described in Patent Document 2 is a method of observing the inside from the main surface (front surface or back surface) of the glass substrate for the purpose of observing defects inside the glass substrate, and the front and back surfaces of the glass substrate are mirror surfaces. Therefore, although the inside of the glass substrate is easy to observe, the shadow caused by the shape of the end of the glass substrate end subjected to R chamfering or C chamfering occurs, and the inside of the glass substrate directly under the end surface is observed. It becomes difficult.

  Conventionally, a method of inspecting a glass substrate end defect by irradiating the glass substrate end opposite to the observer with light and observing the light passing through the inside of the glass substrate from the observer end. There is. This method is effective for small glass substrates, but light travels from one side to the other on a glass substrate with a large area but a small thickness, such as a glass substrate for a flat panel display in recent years. In the meantime, it is greatly attenuated, which hinders observation of the end opposite to the incident.

  Thus, with the conventional inspection method, it is difficult to more reliably detect microcracks that exist directly under the surface of the glass substrate end.

The gist of the present invention is as follows.
(1) The method for inspecting the glass substrate end of the present invention is such that the glass substrate end irradiated with light that is obliquely incident on the main surface of the glass substrate and is totally reflected inside the glass substrate and then travels is obtained. It is characterized by observing from the outside of the part.
(2) The glass substrate end inspection method of the present invention is characterized in that light incident on the glass substrate obliquely intersects with the glass substrate end when viewed from a direction perpendicular to the main surface of the glass substrate. .
(3) When the glass substrate end inspection method of the present invention is viewed from the direction perpendicular to the main surface of the glass substrate, the angle of intersection α of the light incident on the glass substrate intersecting with the glass substrate end is 5 ° to 5 °. It is characterized by being 80 °.
(4) The glass substrate end inspection method of the present invention is characterized in that the angle of intersection α of light incident on the glass substrate intersecting the glass substrate end is changed.
(5) The glass substrate end inspection method of the present invention is such that the range of change of the crossing angle α of light incident on the glass substrate is −5 ° to + 5 ° when the change of the crossing angle α is minimal, and the change is It is characterized in that it is −80 ° to + 80 ° at the maximum.
(6) The method for inspecting the edge of the glass substrate according to the present invention has an incident angle β of light to the main surface of the glass substrate when viewed from a direction parallel to the main surface of the glass substrate and perpendicular to the light traveling direction. However, the present invention is characterized in that the incident light is in a range in which total reflection occurs inside the glass substrate.
(7) The glass substrate edge inspection method of the present invention is characterized in that light is incident on the glass substrate through a refractor placed near the glass substrate edge and having a refractive index close to that of the glass substrate. And
(8) In the glass substrate edge inspection method of the present invention, when the refractive index of the glass substrate is _ng and the refractive index of the refractor is _nr , the difference between _nr and _ng is 0.1 or less. It is characterized by that.
(9) The glass substrate edge inspection method of the present invention is characterized in that the immersion liquid is filled in the gap between the refractive body and the glass substrate.
(10) The glass substrate end inspection method of the present invention is characterized by inspecting the glass substrate end while moving the light incident on the glass substrate and the observation device relatively in parallel with the glass substrate end. And
(11) The glass substrate end inspection method of the present invention is characterized in that the glass substrate is a glass substrate having a thickness of 0.5 mm to 5 mm.

  The glass substrate edge inspection method of the present invention can optically detect defects directly below the edge surface of the display glass substrate, particularly microcracks, which were difficult with conventional inspection methods.

(A) Explanatory drawing of the inspection method of the glass substrate edge part of this invention (figure seen from the direction perpendicular | vertical to the main surface of a glass substrate), (b) Explanatory drawing (glass) of the inspection method of the glass substrate edge part of this invention (Viewed from the direction parallel to the main surface of the substrate and perpendicular to the light traveling direction)

  In the inspection method of the present invention, when inspecting the edge of the glass substrate, light is incident obliquely on the main surface of the glass substrate, and the interior of the glass substrate is advanced by total reflection to irradiate the edge of the glass substrate. And the glass substrate edge part is observed from the outer side.

  FIG. 1A is an explanatory view of the glass substrate end inspection method according to the present invention, as viewed from a direction perpendicular to the main surface 11 a of the glass substrate 11. FIG. 1B is an explanatory view of the glass substrate end inspection method of the present invention, as viewed from a direction parallel to the main surface 11 a of the glass substrate 11 and perpendicular to the traveling direction of the light 12. .

  In the inspection method of the present invention, as shown in FIG. 1A, when viewed from a direction perpendicular to the main surface 11a of the glass substrate 11, incident light (hereinafter also simply referred to as light) 12 to the glass substrate 11 is obtained. However, it is preferable to cross with respect to the glass substrate end portion 13 (not orthogonal). Assuming that the angle at which the incident light 12 and the glass substrate end portion 13 intersect is an intersection angle α, the intersection angle α is 0 ° when the incident light 12 is orthogonal to the glass substrate end portion 13.

  When the incident light 12 on the glass substrate 11 is orthogonal to the glass substrate end portion 13 (intersection angle α = 0 °), the straight traveling light 12 that is not scattered is directly incident on the observation device 14, and therefore weak due to the microcrack 15. Observation of scattered light becomes difficult.

  On the other hand, when the incident light 12 is obliquely intersected with the glass substrate end portion 13 (intersection angle α ≠ 0 °), the strong light 12 that travels straight without being scattered does not directly enter the observation device 14, and therefore the microcrack 15 This makes it easy to observe weak scattered light.

  The intersection angle α at which the incident light 12 intersects the glass substrate end 13 is preferably 5 ° to 80 °. When the crossing angle α is smaller than 5 °, the strong light 12 that travels straight without scattering is easily incident on the observation device 14 as in the case where the incident light 12 is orthogonal to the glass substrate end portion 13. Observation of weak scattered light tends to be difficult.

  On the other hand, if the intersection angle α is larger than 80 °, the amount of light scattered by the microcracks 15 directed to the observation device 14 is reduced, and the detection sensitivity is lowered.

  In the inspection method of the present invention, preferably, the glass substrate end 13 is observed and the microcrack 15 is inspected while changing the intersection angle α between the incident light 12 and the glass substrate end 13. When the direction of the incident light 12 and the direction of the microcracks 15 are in a specific relationship, the microcracks 15 are particularly bright and can be easily detected. Since the direction of the incident light 12 that allows the microcracks 15 to be viewed brightly differs depending on the individual microcracks 15, it is preferable to change the intersection angle α of the incident light 12. Thereby, the microcracks 15 facing various directions can be reliably detected.

  Centering on the direction orthogonal to the glass substrate end 13 (the intersecting angle α at that time is 0 °), the change in the direction of the incident light 12 is represented by the intersecting angle α. When the change range of the angle of intersection is α is −80 ° to + 80 ° is appropriate.

  In the inspection method of the present invention, preferably, as shown in FIGS. 1A and 1B, when the glass substrate end portion 13 of the glass substrate 11 is inspected, the glass substrate end portion 13 is placed in the vicinity. Light 12 is incident on the glass substrate 11 through a refractor (prism) 16 having a refractive index close to that of the glass substrate 11. Incident light 12 on the glass substrate 11 travels with total reflection in the glass substrate 11 and reaches the glass substrate end 13. In this way, since the incident position 17 of the light 12 can be set closer to the glass substrate end 13, the light 12 reaches the glass substrate end 13 with almost no attenuation. Therefore, the scattered light from the microcracks 15 at the glass substrate end 13 can be observed brightly.

When the refractive index of the glass substrate 11 _{n g,} the refractive index of the refractive member 16 and the _{n r,} preferably, the difference of _{n r} and _{n g} is 0.1 or less.

  When the microcrack 15 is present at the glass substrate end portion 13, the light 12 is scattered by the microcrack 15. For this reason, the path of the light 12 is disturbed, and the microcracks 15 can be detected optically.

  In the present invention, since the light 12 is observed from the outside of the end portion 13 of the glass substrate, there are almost no restrictions on the installation position of the observation device 14. Moreover, since the wide range of the glass substrate edge part 13 can be observed at once, the inspection efficiency is good.

When viewed from a direction parallel to the main surface 11a of the glass substrate 11 and perpendicular to the traveling direction of the light 12, the incident light 12 on the glass substrate 11 has a certain incident angle β (FIG. 1B). Shall. The incident angle β is limited to the range in which the incident light 12 causes total reflection inside the glass substrate. The upper and lower limits thereof are the refractive index n _r of the refractor 16, the refractive index _ng of the glass substrate 11, and the refraction of the immersion liquid 18. Determined by optical calculation using the rate n _l . The light that has passed through the refracting body 16 enters the immersion liquid 18 at an incident angle β, enters the immersion liquid 18 at a refractive angle γ, and further enters the glass substrate 11 at a refractive angle δ. Each relationship is represented by the formulas (1) and (2).
γ = Sin ⁻¹ (sin β × (n _r / n _l )) (1)
δ = Sin ⁻¹ (sin γ × (n ₁ / n _g )) (2)
If δ is a condition larger than the critical angle θ _m in the glass substrate 11 as shown by the following formula (3), the light is totally reflected in the glass substrate 11, but within the range satisfying this condition. Determines the upper and lower limits of β.
δ> θ _m = Sin ⁻¹ (n _a / n _g ) (3)
Wherein n _a is the refractive index of the material in contact with the surface opposite to the surface on which the glass substrate 11 is in contact with the immersion liquid 18. If the incident angle β to the glass substrate 11 is smaller than the lower limit, it is difficult to make the light 12 incident on the glass substrate 11 due to restrictions on the apparatus. If the incident angle β to the glass substrate 11 exceeds the above upper limit, the incident light 12 to the glass substrate 11 is not totally reflected and passes through the glass substrate 11, so that the light 12 reaches the glass substrate end 13. Therefore, the glass substrate end 13 cannot be inspected.

  In the inspection method of the present invention, the immersion liquid 18 is preferably filled in the gap between the refractive body 16 and the glass substrate 11. When the flatness of the contact portion between the refracting body 16 and the glass substrate 11 is good, the refracting body 16 can be directly placed on the glass substrate 11 and the light 12 can be incident. Since it does not adhere to the glass substrate 11, the light 12 cannot enter. In such a case, if the immersion liquid 18 is filled in the gap between the refracting body 16 and the glass substrate 11, the refracting body 16 is brought into the same state as being in close contact with the glass substrate 11, and the light 12 is efficiently incident. be able to.

  The refractive index of the immersion liquid 18 is preferably a value between the refractive index of the refractor 16 and the refractive index of the glass substrate 11. In this way, the range of the incident angle β of the incident light 12 is widened, and the loss of the light 12 at the interface between the refractor 16 and the glass substrate 11 is reduced, so that the glass substrate end 13 can be observed brightly. .

  In the present invention, preferably, the glass substrate end 13 is inspected while the incident light 12 and the observation device 14 on the glass substrate 11 and the glass substrate 11 are relatively moved in parallel with the glass substrate end 13. To do. In this way, the glass substrate end 13 can be inspected continuously and efficiently even for a long glass substrate 11.

  The present invention is suitable for inspection of the glass substrate end portion of a glass substrate for flat panel display having a plate thickness of 0.5 mm to 5 mm. The glass substrate for flat panel displays has a very thin plate thickness compared to the area. For this reason, deflection and deformation are likely to occur during conveyance and heat treatment, and damage is easily caused by minute defects. Therefore, the glass substrate end inspection method of the present invention is particularly effectively used.

  A refractor (glass prism) 13 was placed on a glass substrate 11 for a flat panel display having a plate thickness of 1.8 mm at a position 15 mm away from the glass substrate end 13. The refractive index of the glass substrate 11 was 1.55, and the refractive index of the refractor 16 was 1.52. An immersion liquid 18 (refractive index 1.33) was filled in the gap between the glass substrate 11 and the refractor 16.

  The inspection light 12 (illuminance 50,000 Lux) was incident on the refracting body 16 to totally reflect the inside of the glass substrate 11 so as to reach the glass substrate end 13. The incident angle β of the incident light 12 was 48 °. While maintaining the positional relationship between the incident light 12 and the refracting body 16, the direction of the incident light 12 is changed so that the crossing angle α between the incident light 12 and the glass substrate end 13 changes within a range of ± 30 °.

  The glass substrate end portion 13 is imaged with an observation device 14 (microscope), and an image (approximately 80 times) is displayed on the display for visual observation. At the same time, using an image processing device, mainly directly under the surface of the glass substrate end portion 13 The microcracks 15 generated in the test were inspected.

  The inspection of the glass substrate end 13 was performed while the light 12, the refracting body 16, the immersion liquid 18, and the observation device 14 were moved in parallel relative to the glass substrate end 13.

  According to the inspection method of the present invention, the microcracks 15 immediately below the surface of the glass substrate end portion 13 which are difficult to detect by the conventional inspection method can be detected with high sensitivity and efficiency.

  The method for inspecting the edge of the glass substrate of the present invention is suitable for optically inspecting defects, particularly microcracks, directly under the edge surface of a glass substrate for display having a large area and a small thickness.

DESCRIPTION OF SYMBOLS 11 Glass substrate 11a Main surface 12 of glass substrate Incident light, light 13 Glass substrate edge part 14 Observation apparatus 15 Microcrack 16 Refraction body 17 Light incident position 18 Immersion liquid

Claims (11)

  A glass substrate characterized by observing, from the outside of the glass substrate end portion, an end portion of the glass substrate that is obliquely incident on the main surface of the glass substrate and is irradiated with light that travels by being totally reflected inside the glass substrate. Edge inspection method.   2. The glass substrate end portion according to claim 1, wherein when viewed from a direction perpendicular to the main surface of the glass substrate, the light incident on the glass substrate obliquely intersects with the glass substrate end portion. Inspection method.   The crossing angle α at which the light incident on the glass substrate intersects the edge of the glass substrate when viewed from a direction perpendicular to the main surface of the glass substrate is 5 ° to 80 °. 2. The inspection method of the edge part of the glass substrate of 2.   The inspection method of the glass substrate edge part of Claim 2 or 3 which changes the crossing angle (alpha) which crosses the said glass substrate edge part of the said light which injects into the said glass substrate.   The range of change of the intersection angle α of the light incident on the glass substrate is −5 ° to + 5 ° when the change of the intersection angle α is minimum, and −80 ° to + 80 ° when the change is maximum. The inspection method of the glass substrate edge part of Claim 4 characterized by these.   When viewed from a direction parallel to the main surface of the glass substrate and perpendicular to the traveling direction of the light, the light entering the main surface of the glass substrate is incident at an incident angle β, and the incident angle β is 6. The method for inspecting an end portion of a glass substrate according to claim 1, wherein the light is within a range that causes total reflection inside the glass substrate.   The light is incident on the glass substrate through a refractor placed near the edge of the glass substrate and having a refractive index substantially equal to the refractive index of the glass substrate. The inspection method of the glass substrate edge part of crab. The refractive index n _g of the glass _substrate, and the refractive index of the refractive member has a n _r, the difference between n _r and n _g is equal to or more than 0.1, the glass according to claim 7 Inspection method for substrate edge.   The inspection method for an end portion of a glass substrate according to claim 7 or 8, wherein an immersion liquid is filled in a gap between the refractive body and the glass substrate.   The said glass substrate edge part is test | inspected, moving the said light which injects into the said glass substrate, and the said observation apparatus relatively in parallel with the said glass substrate edge part, The any one of Claim 1 to 9 characterized by the above-mentioned. The inspection method of the glass substrate edge part of crab.   The glass substrate end inspection method according to any one of claims 1 to 10, wherein the glass substrate is a glass substrate having a thickness of 0.5 mm to 5 mm.

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