JP3480176B2 - Glass substrate front / back defect identification method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method for identifying defects existing on the front and back surfaces of a glass substrate for a liquid crystal panel. 2. Description of the Related Art A large number of TFT elements are formed on the surface of a TFT substrate constituting a liquid crystal panel using a glass substrate as a material. If a defect such as a scratch is present on this surface, a TFT element is not formed satisfactorily in that part,
Since the quality of the substrate is hindered, a defect inspection apparatus inspects the presence or absence of a defect and takes necessary measures. In the defect inspection device, by a detection optical system, a laser beam is projected on a glass substrate, scattered light of the defect is received by a light receiver to detect the defect, and the detection signal is processed by a data processing unit. Defect data obtained by calculating the size of a defect and adding a coordinate value at which the defect exists is output. There are various types of defects in glass substrates.
As typical examples, there are three kinds of foreign matters and scratches present on the front surface or the rear surface, and bubbles existing inside the substrate. Of these, foreign matter on the front surface and scratches are inconvenient defects because they impair the quality of the TFT element to be formed, but foreign matter on the back surface and scratches and bubbles inside are harmful unless they are too large. Can be ignored because there is no Thus, the three types of defects are based on the type of TFT.
Therefore, it is necessary to specify these types, but the above-described defect inspection apparatus does not have a function of determining the type. On the other hand, the inventor of the present invention has devised a method of detecting each defect and determining the type of the defect, and has filed a patent application for “a method of determining the type of defect on a glass substrate”. [0004] The above-described defect inspection apparatus detects both the front and rear surface defects, and the above-described defect type determination method also employs any of the two-sided defect detection methods. It also detects defects. However, surface defects impair the quality of the TFT element, and appropriate measures are taken. However, surface defects are harmless because they are not directly related to TFT, and it is necessary to identify them for substrate management. It is. Conventionally, an effective method for distinguishing a front surface defect from a rear surface defect has not been put to practical use yet. SUMMARY OF THE INVENTION It is an object of the present invention to detect a defect in a glass substrate and reliably identify whether the defect is present on the front surface or the back surface. SUMMARY OF THE INVENTION The present invention is directed to a method for identifying front and back defects of a glass substrate, which solves the above-mentioned problems. by projecting beams L _T, the light spot S _P on its surface
Forming a by laser beam L _T refracted by the surface to form a light spot S _P 'on the back. Symmetrically to the light projecting system, the spatial filters of the light receiving system provided at a light receiving angle of about 45 ° cut off the specularly reflected lights L _H and L _R of the two light spots _SP and _SP ′ from the front and back surfaces. the scattered light S _H of the defect K _H at the position of the light spot S _P, scattered light S _R of the defect K _R at the position of the light spot S _P ', by an imaging lens, a CCD image sensor, both light spot S _P, 2 pieces of specific elements corresponding to the S _P 'e _H, to form an image on e _R. The presence / absence of the defect signals D _H and D _R output by the two elements e _H and e _R respectively is determined by “1”.
As "0", each identifying the following _{conditions: (D H: "1"} , D R: "0"); K H ......... condition _{(1) (D H: "} 1", D R: "1 ); K _H ... Condition (2) (D _H : “0”, D _R : “1”); K _R ... Condition (3), the front surface defect K _H and the rear surface defect K _R. Is to be identified. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the principle of a front / back defect identification method according to the present invention will be described. In FIG. 1, the thickness of the glass substrate 1 is h, the surface on which the TFT is formed is H, the defect existing in _H is K _H , the rear surface is R, and the defect existing in _R is KR. The laser beam L _T to the substrate 1, and projected at an incident angle theta ₁ of 45 °, to form a light spot S _P to the surface H. The laser beam L _T is also to be projected on the rear surface R is refracted by the surface H to form a light spot S _{P '.} In this case, the formation position of both light spots _SP and _SP 'is
The refractive angle of the laser beam L _T by the surface H, spaced by a predetermined distance d which is determined by the thickness h of the substrate 1. Both the light spot _{S P,} of _{S P} ', the surface H and back R due to the positive reflection light _{L H,} are blocked by the spatial filter F and _{L R.} Defect _KH
There were scattered scattered light S _H to be present at the position of the light spot S _P, scatters the scattered light S _R and defects K _R is present in the position of the light spot S _{P '.} Both the scattered light _{S H,} the _{S R,} the light receiving angle theta ₂ is received by the CCD sensor through 45 ° of the imaging lens, both the defect _{K H,} image _{K R} are both the light spot _{S P,} spacing _{S P} ' spaced by a distance d 'corresponding to the d, 2 pieces of specific elements _{e H} of the CCD sensor, is focused on _{e R,} both elements _{e H, e R} defect _{K H,} the defect signal _{D H} for _{K R,} D _R to be output, respectively. Therefore, both the defect signal _{D H,} the presence or absence of _{D R,} respectively "1", when "0", the identification _{conditions: (D H: "1"} , D R: "0"); K H ...... conditional _{(1) (D H: "} 0", D R: "1"); it is clear _{that K R} ......... condition (3) is satisfied. However, both defects K _H ,
K _R is, when present light spot _{S P,} the position of the _{S P} 'at the same _{time, (D H: "1"} , D R: "1"); but _{K H} ......... condition (2) is satisfied , the back surface of the defect K _R is ignored, there is no problem because the defect K _H of the surface are identified. In addition, the defect K _H
Due because the size of the large, when the intensity of the scattered light S _H is large, which is reflected by the rear surface R is refracted by the surface H, in the same way as the light spot S _{P ',} device and re refracted at the surface H e _R may form an image. Again, both the defect signal _{D H,} because _{D R} both become "1",
Condition (2) holds. Thus, a virtual image defect is generated on the back side.
Irradiate a laser beam that emits light from one side of the front side.
After obtaining the respective detection states, under the conditions (1) and (3),
Is not detected by the other party,
Judge surface defects and back surface defects.
Those that generate a surface virtual image are determined as surface defects. This judgment
As a result, the original surface defect enters the front side defect,
The backside virtual image defect is excluded from the detection of the defect. Note that in reality
If there is a real defect at the same position on the front and back, stochastically
Low, so ignore surface defects in this case and only surface defects
There is no problem in practice. Thus, the defect K _H of the front surface and the back surface of the defect K _R is reliably identified. In addition,
This has been confirmed by trial experiments. by the way,
The reason that the condition (2) is necessary as the identification condition is that, as a configuration of the present invention, the reflected light from the back side can be received, and the scattered light is received to obtain a front and back defect detection signal. Therefore, it is necessary to project relatively strong light on the glass surface. Therefore, unless the condition (2) is added to the identification criterion, the actual front / back determination is not sufficient.
The condition (2) is a detection state in which there is a defect on both the front and back sides, but this state does not mean that a large number of defects are detected, but may be determined depending on the detection target.
For example, in the case of a glass substrate for a liquid crystal panel, when the condition (2) is satisfied, it is determined that the surface-side defect is present. The defect on the front side of the liquid crystal panel impairs the quality, but the defect on the back side of the point has almost no influence. FIG. 2 shows the configuration of a defect detection / front / back identification device 10 according to an embodiment of the present invention. However, this embodiment is configured to be applied to a glass substrate whose defect type is distinguished by the above-mentioned “method of determining defect type of glass substrate”. FIG.
1, the defect detection / front / back identification device 10 includes a detection optical system 2, an XY stage 3 on which the glass substrate 1 is mounted, a control unit 4, a data processing unit 5, and a defect data memory 6. [0008] detecting optical system 2 and the light projecting system 21 consists of a light receiving system 22, the laser beam L _T by the laser diode (LD) 211 of the light projecting system 21 is generated, it is focused by the focusing lens 212, and then the cylindrical lens 213 the X direction is focused, is projected at an incident angle theta ₁ of approximately 45 ° to the substrate 1, to form a light band L _B having a width w and Y direction length l of the X-direction to the surface H, Further, the light is refracted by the front surface H to form a light band L _B ′ on the rear surface R. Ryohikaritai L _B, surface H and back R of L _B '
Are reflected light L _H and L _R by the condenser lens 221.
, Are sequentially reflected by mirrors 222 and 223, are imaged by the imaging lens 224 on one of the elements e of the CCD linear sensor 225, and the output signal of the imaged element e is transmitted to the control unit 4.
The moving mechanism 42 is driven by a focus control signal output from the focus control circuit 41, and the detection optical system 2 is moved in the Z direction to focus the light receiving system 22. On the other hand, both the defect K _H, K _R of the scattered light S _H, S _R is the condenser lens 22
The light is condensed by 1 and is received by the CCD image sensor 227 via the imaging lens 226. CCD image sensor 22
The 7, the optical band L _B, and the element e is arranged in a matrix in the range of 'width corresponding to w' L _B and the length l ', both the scattered light S _H, S _R
Are correctly imaged on the specific elements e _H and e _R described above in the lateral direction. In the glass substrate 1 to be identified, both the front surface, the back surface, and the inside defect are detected by the above-described “method of determining the defect type of the glass substrate”, the defect types are distinguished, and the XY coordinates of each defect are determined. The value is known. The XY coordinate values of the foreign matter and the scratches are stored in the defect data memory 6 in advance. The data processing unit 5 comprises an image memory 51, a microprocessor (MPU) 52, and a printer 53.
In the PU 52, a front / back identification program PG1, a data editing program PG2, and a control signal generation program PG3 are set. The XY coordinate values of the foreign matter and the scratches stored in the defect data memory 6 are read out by the PG 3, and a control signal generated by the readout is supplied to the XY movement control circuit 43 of the control unit 4 and placed on the XY stage 3. substrate 1 is moved stepwise in the X or Y direction, the foreign matter or scratches are stopped at the position of the light band L _B or L _B '. [0011] Scattered light S _H , S _{R of} foreign matter or scratches
A particular element e _H in the vertical and horizontal direction of the CCD image sensor 227 by the, e _R is focused on, which are sequentially scanned for each row the two elements e _H, defects than e _R signal D _H, D _R
Is output and stored in the image memory 51. In MPU 52, PG1 defect signal D _H of each row of the image memory 51, the presence or absence of D _R is detected by the identification conditions (1) -
According to (3), whether the foreign matter or the scratch is present on the front surface H or the rear surface R is identified, and the identification data is edited by the PG2 and printed by the printer 53. [0012] As the above description, the front and back defect identification method of the present invention, the laser beam L _T projected at an incident angle of approximately 45 ° with respect to the glass substrate, the light formed on the surface and the spot S _P, the laser beam L _T refracted by the surface
Paying attention to the fact that the light spot S _P ′ formed on the back surface makes a constant interval, and the scattered light S _H of the surface defect K _H ,
The scattered light S _R of the rear surface of the defect K _R, and focused on two specific elements of the CCD sensor, each of the defect signal D _H, the presence or absence of D _R, reliably identify the defect K _H and defect K _R The effect of contributing to the production and management of a glass substrate for a liquid crystal is significant.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating the principle of a method for identifying front and back defects according to the present invention. FIG. 2 is a configuration diagram of a defect detection / front / back identification device according to an embodiment of the present invention. [Description of Signs] 1 ... glass substrate, 2 ... detection optical system, 21 ... light projection system, 211 ...
LD, 212: focusing lens, 213: cylindrical lens, 22: light receiving system, 222, 223: mirror, 224, 226: imaging lens, 225: CCD linear sensor, 227: CCD image sensor, 3: XY stage, 4 ... control unit, 41 ... focus control circuit, 42 ... moving mechanism, 43 ... XY movement control circuit 5 ... data processing unit, 51 ... image memory, 52 ... MPU, 53 ...
Printer, 6 ... defect data memory, 10 ... the invention defect detection and side ID device by, H ... surface of the substrate, R ... back surface of the substrate, defects in K _H ... surface, K _R ... back surface of the defect, L _T ...
The laser beam, the light spot S _P ... surface, S P _'... rear surface of the light spot, L _B ... surface of the light spot, L _B' ... back surface of the light spot, L _H, L _R ... regularly reflected light, S _H ... scattered light of the defect K _H, scattered light S _R ... defect _{K R, e H, e R} ... CCD image specific two elements of the sensor.

Continuation of the front page (72) Inventor Noboru Kato 3-16-3 Higashi, Shibuya-ku, Tokyo Hitachi Electronics Engineering Co., Ltd. (56) References JP-A-52-14477 (JP, A) JP-A-3-3 276005 (JP, A) JP-A-5-157701 (JP, A) JP-A-6-510856 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1333 G01N 21 / 88

Claims (1)

(57) approximately 45 with respect to glass substrates by [Claims 1. A light projecting system
At an incident angle of ° by projecting a laser beam L _T, the Gala
On the surface of the scan substrate to form a light spot S _P, by the laser beam L _T refracted at the surface, to form a light spot S _{P 'to} <br/> back surface of the glass substrate,-projecting optical system and symmetrically manner, by the light receiving system spatial filter provided in the light-receiving angle of approximately 45 °, to block both said light spot S _P, of S _{P ',} specularly reflected light L _H by the surface and the back surface, the L _R, light Spot _SP
A scattered light _{S H} of the defect _{K H} at position, the scattered light _{S R} of the defect _{K R} in the position of the light spot _{S P} ', by an imaging lens, a CCD image sensor, both said light spot _{S P} , _{S P} 'in the corresponding two specific elements _{e H,} imaged on _{e R,} the both elements _{e H,} the defect signal _{D H where e R} outputs respectively, the presence or absence of _{D R,} respectively "1" , "0",
Each identification the following _{conditions: (D H: "1"} , D R: "0"); K H ......... condition _{(1) (D H: "} 1", D R: "1"); K H ... ...... condition _{(2) (D H: "} 0", D R: "1"); K by _R ......... condition (3), wherein the defect _{K H} of the surface of the glass substrate Gala
And wherein the identifying and the back of the scan board defects K _R, front and back defect identification method of a glass substrate.