JP2004233338A - Defect detection method of disc substrate, apparatus for the same, and method for manufacturing substrate for optical disc - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defect detection method for discriminating and detecting defects of the surface and the cross section of a disc substrate as a disc recording medium, comprising a translucent material by using an identical optical system, and to provide an apparatus for the method and a method for manufacturing an optical disc. <P>SOLUTION: While the defect detection apparatus 10 rotates the disc substrate 12, an irradiated light enters internally and obliquely from its surface 12A to a normal of the surface 12A in one rotational direction by using an illumination apparatus 18. The reflected light, reflected by a back face 12B of the disc substrate 12 sequentially enters into a line camera 20. The distance between an abnormal part (real image) due to the defect on the optical path of the entering light and an abnormal part (shadow) on the optical path of the reflection light is detected. It discriminates whether the defect is the surface defect or the internal defect, in response to the distance. The disc substrate, having only the surface defect, is removed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method for detecting a defect in a disk-shaped substrate serving as a disk-shaped optical recording medium (optical disk) such as a CD (compact disk) and a DVD (digital versatile disk), an apparatus therefor, and a method for manufacturing an optical disk substrate. About.

  Optical disks such as CDs and DVDs have been widely used as recording media for recording data and images. In recent years, optical recording media capable of recording / reproducing even larger amounts of data and long-time images have been used. And the recording density of optical discs is being improved.

  In order to increase the recording density of the optical disc, it is necessary to reduce the beam spot diameter of the recording / reproducing laser beam irradiated on the optical disc. The beam spot diameter of the laser beam depends on the wavelength of the laser beam and the lens. Therefore, it is necessary to use a laser beam having a short wavelength and a lens having a large numerical aperture to record and reproduce data on an optical disk.

  However, when a lens having a large numerical aperture is used, the focal length of the laser beam becomes short. Therefore, in the case of a substrate such as a CD or DVD having a thickness of about 1.2 mm, the recording layer is irradiated with the laser beam through the substrate. I can't. For this reason, it has been proposed to form a thin light transmitting layer of about 0.1 mm on the recording layer and to irradiate the recording layer with laser light through the light transmitting layer.

  As described above, since a recording / reproducing laser beam is applied to a CD or DVD through the substrate, defects due to both foreign substances on the surface and inside of the substrate and agglomerates of the substrate material may occur during recording / reproduction. Has a negative effect. For this reason, when inspecting a substrate during the production of an optical disk, a defective substrate is removed regardless of whether the defect exists on the surface or inside the substrate.

  As a defect inspection apparatus and inspection method for the surface of a disc-shaped substrate in a process of manufacturing an optical disc, a surface to be inspected of the disc-shaped substrate is irradiated with a light beam, and reflected light or transmitted light of the light beam is applied to the outer periphery from the center of the disc-shaped substrate. By receiving light by light receiving means in which a large number of pixels are arranged in a line toward the light, taking in information from the light receiving means while rotating the disc-shaped substrate, and determining a normal part and a defective part based on the information. There is an inspection method and apparatus for inspecting the disk-shaped body for defects (for example, see Patent Document 1).

  Here, the light receiving means is a line camera, which scans one round by the line camera while rotating the disc-shaped substrate, processes the video output signal by an image processing device, and detects a defect by the CPU based on the processing information. Is analyzed.

  For example, an internal defect of a substrate in a disk-shaped recording medium is detected by transmitted light, in addition to detecting a surface defect by reflected light.

JP 2001-241931 A

  However, with respect to an optical disc that irradiates recording / reproduction laser light through the light transmission layer, since the recording / reproduction laser light does not enter the substrate, defects inside the substrate adversely affect the recording / reproduction. Will not be given. However, defects existing on the surface of the substrate on which the recording layer is provided adversely affect the recording layer provided thereon. For this reason, in the inspection process of the substrate during the production of the optical disk, it is sufficient to remove only the substrate having a defect only on the surface of the substrate on which the recording layer is provided.

  However, in the conventional inspection method, there was no method for easily determining whether a defect was on the surface of the substrate or inside the substrate. Therefore, a substrate having a defect only on the inside was also removed, which reduced the production yield. It was.

  The present invention has been made in view of the above problems, and detects and detects defects on the surface of a disk-shaped substrate and internal defects, a method for detecting a defect on a disk-shaped substrate capable of improving the production yield, An object of the present invention is to provide an apparatus and a method for manufacturing an optical disk.

  The inventor of the present invention has conducted intensive studies and found that when a disc-shaped substrate made of a light-transmitting material is rotated, light is incident obliquely from the front surface of the disc-shaped substrate, and when light reflected on the back surface is received, a defect occurs on the optical path of the incident light. And when it is on the optical path of the reflected light, and it is found that the difference between the two detection timings is different between the surface defect and the internal defect. Further, it is found that when the distance in the disk-shaped substrate rotation direction in these two detections is a fixed value, the defect is a surface defect, and when the distance is less than the fixed value, the defect is an internal defect. It was found that the substrate could be removed and the yield could be improved.

  That is, the above object is solved by the following present invention.

  (1) A process in which irradiation light is incident on a surface of a disk-shaped substrate made of a light-transmitting material while rotating the disk-shaped substrate in one direction of rotation with respect to a perpendicular to the surface, and When the reflected light on the back surface of the irradiated light incident on the back surface is received with a time delay sequentially from a direction inclined to the opposite side to the irradiated light with respect to the perpendicular, and the received reflected light amount is smaller than a set value. Or, when it is large, it is determined as an abnormal part. When there are two abnormal parts with a time difference, it is determined whether or not these two abnormal parts are similar. Two abnormal parts, the distance in the rotational direction of the disk-shaped substrate, a step of measuring by image processing, a step of determining whether the distance is a set value, and a surface defect if the distance is a set value Discriminating a disc Defect detection method of a substrate.

  (2) A process in which irradiation light is incident on a surface of a disc-shaped substrate made of a light-transmitting material while rotating the disc-shaped substrate in one direction of rotation with respect to a perpendicular to the surface, and When the reflected light on the back surface of the irradiated light incident on the back surface is received with a time delay sequentially from a direction inclined to the opposite side to the irradiated light with respect to the perpendicular, and the received reflected light amount is smaller than a set value. Or, when it is large, it is determined as an abnormal part. When there are two abnormal parts with a time difference, it is determined whether or not these two abnormal parts are similar. Measuring the distance in the rotational direction of the disc-shaped substrate between the two abnormal portions by image processing, and measuring the position of the defect in the thickness direction within the disc-shaped substrate. Detection method.

  (3) The step of determining as an abnormal part is a step of detecting an abnormal point that occurs when the amount of reflected light received is smaller or larger than a set value, and the step of detecting the abnormal point corresponding to a position on the surface of the disk-shaped substrate. (1) displaying the map on a map and determining whether the displayed set of abnormal points has a shape as an abnormal portion. Defect detection method.

  (4) From the center to the outer periphery of the disc-shaped substrate, the reflected light is received by a line camera in which a number of pixels are arranged in the radial direction of the disc-shaped substrate, and the information captured by the line camera is image-processed. The method for detecting a defect of a disk-shaped substrate according to (1), (2) or (3), wherein a distance between two abnormal portions is measured.

(5) The set value L (mm) serving as a criterion for determining the distance between the two abnormal portions is such that the refractive index of the light transmitting material is n, the thickness is t (mm), and the disk-shaped substrate of the irradiation light when the incident angle _{θ 2, n = Sinθ 2 /} Sinθ 1 to the surface, L = 2tTanθ ₁ and the possible, characterized in (1) to (4) any defect detection method of the disk-shaped substrate.

  (6) The method for detecting defects of a disc-shaped substrate according to any one of (1) to (5), wherein the wavelength of the irradiation light is 600 to 700 nm.

  (7) An incident angle of the irradiation light, which is an angle with respect to a normal to the surface of the light transmitting material layer, is set to 15 ° to 85 °, preferably 30 ° to 45 °. 6) The method for detecting a defect of a disc-shaped substrate according to any one of 6).

  (8) A rotation support device for mounting and rotating a disk-shaped substrate formed of a light-transmitting material, and one surface of the disk-shaped substrate in a direction of rotation with respect to a perpendicular to the surface. Irradiation device that irradiates the irradiation light obliquely, and simultaneously or sequentially measures the center of the disc-shaped substrate to the outer periphery in the radial direction while rotating the disc-shaped substrate, and the irradiation light is irradiated on the surface of the disc-shaped substrate. And a light detecting device that sequentially receives the reflected light generated on the back surface thereof with a time lag, and determines that the reflected light received by the light detecting device is abnormal when the amount of reflected light is smaller or larger than a set value. In addition, when there are at least two abnormal portions with a time lag, it is determined whether or not these abnormal portions have similar shapes. If the abnormal portions have similar shapes, the disk-shaped substrate rotation direction between the two abnormal portions is determined. Measure distance That the image processing apparatus and the measured distance defect detection device of a disk-shaped substrate made have, a determining unit that there is surface defects in the case of setting values.

  (9) The image processing apparatus detects an abnormal point when the amount of reflected light received by the photodetector is smaller or larger than a set value, and the abnormal point corresponds to a position on the surface of the disk-shaped substrate. (8) The disc-shaped substrate defect detection device according to (8), wherein the defect detection device is displayed on a map and determines whether or not the displayed set of abnormal points has a shape as an abnormal portion.

  (10) The disk according to (8) or (9), wherein the photodetector is a line camera in which a number of pixels are arranged in a radial direction of the disk-shaped substrate from a center to an outer periphery of the disk-shaped substrate. Defect detection device for substrate.

(11) In the determination device, the set value L (mm) serving as a criterion for determining the distance between the two abnormal portions is such that the refractive index of the light transmitting material is n, the thickness is t (mm), and the irradiation is when the incident angle to the disk-shaped substrate surface of the light was _{θ 2, n = Sinθ 2 /} Sinθ 1, characterized in that it is set to be _{L = 2tTanθ 1 (8),} (9) Or the defect detection device for a disc-shaped substrate according to (10).

  (12) On the optical path of the irradiation light from the irradiation device to the disc-shaped substrate, a band-pass filter that transmits only light in a wavelength region of a predetermined width centered on a specific wavelength is provided. The defect detection apparatus for a disc-shaped substrate according to any one of (1) to (11).

  (13) A polarizing plate for polarizing the light transmitted through the bandpass filter to one of left-handed or right-handed circularly polarized light and two linearly polarized lights whose polarization planes are orthogonal to each other is provided. (12) A light receiving side polarizing plate is provided in the reflected light path leading to the photodetector, in which the reflected light transmits only the polarized light having a phase shifted by π from the polarized light passing through the polarizing plate. Defect detection device for disk-shaped substrates.

  (14) A process of continuously forming a disc-shaped substrate from a light-transmitting material, and irradiating the disc-shaped substrate with the irradiation light while rotating the disc-shaped substrate in one of the rotation directions with respect to a perpendicular to the surface. The process of incidence, and the irradiation light incident on the disc-shaped substrate from the front surface, the reflected light on the back surface, from the direction inclined to the opposite side to the irradiation light with respect to the perpendicular, received the light sequentially with a time shift. A step of judging an abnormal portion when the amount of reflected light received is smaller or larger than a set value; and, when two abnormal portions are out of time, whether or not these two abnormal portions have similar shapes. Determining the distance between these two abnormal portions when they have similar shapes in the rotational direction of the disc-shaped substrate by image processing, and determining whether or not the distance is a set value. , Surface defects when the distance is the set value And litho determining step, wherein the disk-shaped substrate other than where it is determined that there is a surface defect, at least a recording layer and a method of producing an optical disk consisting comprises a process, the forming the light transmission layer in this order.

  (15) A process of continuously forming a disc-shaped substrate from a light-transmitting material, and irradiating the disc-shaped substrate with the irradiation light tilted in one of the rotation directions with respect to a perpendicular to the surface while rotating the disc-shaped substrate. The process of incidence, and the irradiation light incident on the disc-shaped substrate from the front surface, the reflected light on the back surface, from the direction inclined to the opposite side to the irradiation light with respect to the perpendicular, received the light sequentially with a time shift. A step of judging an abnormal portion when the amount of reflected light received is smaller or larger than a set value; and, when two abnormal portions are out of time, whether or not these two abnormal portions have similar shapes. Determining the position of the defect in the thickness direction in the disk-shaped substrate by measuring the distance between these two abnormal portions in the rotational direction of the disk-shaped substrate when they are similar to each other by image processing. Except that it was determined that there was a surface defect The disk-shaped substrate, at least a recording layer and a method of producing an optical disk consisting comprises a process, the forming the light transmission layer in this order.

  (16) The step of determining the abnormal portion is a process of detecting an abnormal point that occurs when the amount of reflected light received is smaller or larger than a set value, and the process of detecting the abnormal point with a position on the surface of the disk-shaped substrate. (14) or (15) the method of manufacturing an optical disc according to (14) or (15), further comprising the step of: displaying on a map and determining whether or not the displayed set of abnormal points has a shape as an abnormal portion. .

  (17) The line camera in which a large number of pixels are arranged in the radial direction of the disk-shaped substrate from the center to the outer periphery of the disk-shaped substrate receives the reflected light, and the information captured by the line camera is image-processed. The method for manufacturing an optical disc according to any one of (14) to (16), wherein a distance between two abnormal portions is measured.

(18) The set value L (mm) serving as a criterion for determining the distance between the two abnormal portions is such that the refractive index of the light-transmitting material is n, the thickness is t (mm), and the disk-shaped substrate of the irradiation light when the incident angle _{θ 2, n = Sinθ 2 /} Sinθ 1 to the surface, L = 2tTanθ ₁ and was characterized by the (14) to one of optical disc manufacturing method (17).

  Since the present invention is configured as described above, defects on the surface of the disc-shaped substrate and defects on the inside thereof can be reliably determined and detected by the same optical system, and the production yield of the optical disc can be improved. It has an excellent effect that it can be performed.

  As shown in FIG. 1, a disk-shaped substrate defect detection apparatus 10 according to the preferred embodiment of the present invention constitutes a part of an optical disk manufacturing apparatus 50 (see FIG. 8) and is manufactured by a substrate manufacturing apparatus 60. Then, a disk-shaped substrate 12 made of a light-transmitting material (an optical disk formed by forming various films in the next step) is placed with its film-forming side exposed and rotated. In FIG. 1, a supporting device 16, an irradiating device 18 for irradiating the irradiating light obliquely from above with respect to the film-forming side, and a center to an outer periphery of the disc-shaped substrate 12 while rotating the disc-shaped substrate 12. Are simultaneously measured in the radial direction, and a line camera 20 for receiving reflected light of the irradiation light from the irradiation device 18 on the front surface and the back surface (described in detail later) of the disc-shaped substrate 12, and a reflection light received by the line camera 20. Light intensity When a dark point generated when the value is smaller than the set value or a bright point generated when the value is larger than the set value due to a defect on the surface or inside of the disk-shaped substrate 12 is detected as an abnormal point, and when the abnormal point is arranged on the substrate surface, an abnormal A set formed by points is regarded as an abnormal part. Therefore, the shape of the abnormal portion indicates the size and shape of the defect.

  When the abnormal portion is detected and the abnormal portion is detected twice with a time shift, it is determined whether or not the shapes of the two abnormal portions are similar. If the abnormal portions are similar, the two abnormal portions are determined. An image processing device 22 for measuring the distance in the rotational direction of the disk-shaped substrate, and a CPU 24 which is a determination device for determining that there is a surface defect when the measured distance is a set value.

  In FIG. 1, reference numeral 26 denotes a motor constituting a part of the rotation support device 16, reference numeral 28 denotes a motor control device for controlling the rotation speed of the motor 26, reference numeral 30 denotes a display for displaying the judgment result in the CPU 24, reference numeral 32 Is a printer that outputs the same determination result, 34 is a transport device that transports the disc-shaped substrate inspected according to the determination result of the CPU 24 to the next process or discharges it as a defective product, and 36 is a determination result signal from the CPU 24 to the transport device 34. The sequencer to be sent is shown. The rotation support device 16 is provided on an inspection table 40 described later.

  The disc-shaped substrate 12 is a polycarbonate (PC) substrate as shown in FIG. 2 with a partial cross-sectional view schematically enlarged. The reflective film 14A, the heat-resistant protective film 14B, the recording film 14C, the interface layer 14D, the heat-resistant protective film 14E, and the light-transmitting layer 14F are formed, and further, the outermost hard coat layer 14G is formed to form the optical disc 14.

  In a step (film formation line 70: see FIG. 8) after the disk-shaped substrate 12 is inspected by the defect detection device 10, the reflection film 14A to the hard coat layer 14G are formed.

  As shown in FIG. 3, the irradiating device 18 irradiates a band-shaped irradiation region 19 that traverses from the inner circumference to the outer circumference of the disc-shaped substrate 12 in a straight line in the radial direction. As shown in FIG. 4, the irradiation device 18 includes a light source 18A such as a halogen lamp, and band-pass filters 18B and SC arranged in this order on the optical path of irradiation light from the light source 18A to the disc-shaped substrate 12. (Sharp cut) A filter 18C, a linear polarizing plate 18D, and a λ / 4 phase difference plate 18E are included. The right-handed or left-handed circularly polarized light is incident on the surface of the disk-shaped substrate 12 as irradiation light. .

  Here, the band-pass filter 18B is designed to transmit light of a certain bandwidth with a peak at a wavelength of 650 nm, and the SC filter 18C is designed to cut light having a wavelength of less than 610 nm.

  The line camera 20 has a large number of pixels (for example, 4096 pixels) arranged in a line from the center of the disc-shaped substrate 12 to the outer periphery thereof, and a video output signal is provided in accordance with the amount of reflected light received for each pixel. Is output to the image processing device 22.

  On the optical path of the reflected light between the line camera 20 and the disc-shaped substrate 12, a circularly polarizing plate 20A is arranged. The circularly polarizing plate 20A reflects the left-handed or right-handed circularly polarized light irradiated from the irradiation device 18 on the back surface of the disc-shaped substrate 12, and changes the phase by π to the right-handed or left-handed circularly polarized light. Only the transmission is allowed.

  As shown in FIG. 5, the arrangement of the irradiation device 18 and the line camera 20 is such that the irradiation light I from the irradiation device 18 enters the inside from the front surface 12A of the disc-shaped substrate 12 and is reflected by the back surface 12B. The light R is incident on the line camera 20.

Here, the irradiation light I is inclined in one of the rotation direction, that is, the tangential direction of the disc-shaped substrate 12 with respect to the normal to the surface 12A, and the angle with respect to the normal to the surface 12A of the disc-shaped substrate 12, that is, the incident light. The angle θ ₂ is set to 15 ° to 85 °. Within this angle range, the irradiation light enters the cross section from the front surface 12A of the disc-shaped substrate 12 without being totally reflected, and is reflected on the back surface 12B. The reflected light is received by the line camera 20 at a position inclined with respect to a perpendicular to the surface 12A, opposite to the irradiation light.

In particular, real and shadow which is measured so as to measure not to overlap the defect distance is large between (see below), it is necessary to increase the theta _2, also, when too large theta _2, real and shadow Since the distance becomes large and the amount of data processing for determining these similar shapes becomes large, θ ₂ is preferably 30 ° to 45 °.

  For example, as shown in FIG. 6, the image processing device 22 sets each pixel number of the line camera 20 on the horizontal axis from the center side of the disc-shaped substrate 12 to the outer peripheral side, and the light reception amount (reflected light amount) on the vertical axis. Based on a low set value (low threshold level) and a high set value (high threshold level) of the reflected light amount, when the reflected light amount is smaller than the low threshold level, this is detected as a dark point. FIG. 7 shows the result of the judgment obtained by detecting the amount of light received by the pixels of the 1-4096 pixel numbers of the line camera, and the line camera sequentially shifts the time (scans) to receive light. The determination results obtained by detecting the amounts are displayed vertically as a map. The determination result for one scan of one pixel is displayed in one square (one dot) in FIG. The position on the entire surface of the disc-shaped substrate is represented by 4096 × 24000 dots. An aggregate of dark spots detected as shown in FIG. 6 is recorded as an abnormal portion of 3 dots in the radial direction and 4 dots in the scan direction, for example, as shown in FIG. And the distance between them in the circumferential direction of the disc-shaped substrate is calculated. When the light transmittance of the defect is larger than the material of the disk-shaped substrate 12, for example, when the amount of reflected light is larger than a high set value (high threshold level), it is detected as a bright point, and the aggregate thereof is also regarded as an abnormal part. Become.

As will be described later, the preceding (upper) abnormal portion (a collection of dark spots or a collection of bright spots; the same applies hereinafter) D ₁ in FIG. 7 is a real image, and the following (lower) abnormal portion D ₂ is a shadow. Be recognized.

The CPU 24 compares the distance L between the _two abnormal portions D ₁ and D ₂ with a preset set reference value. The determination result is sent to the transfer device 34 via the sequencer 36, and based on the input result information, the transfer device 34 sends the inspected disk-shaped substrate 12 to a subsequent process or discharges the inspected disc-shaped substrate 12 from the line as NG. Have been.

Here, the set value L (mm) serving as a criterion for determining the distance between the two abnormal portions is such that the refractive index of the disk-shaped substrate 12 is n, the thickness is t (mm), and when the incident angle to the surface 12A of the substrate is _{θ 2, n = Sinθ 2 /} Sinθ 1, there as L = 2tTanθ _1.

  As shown in FIG. 8, the transfer device 34 includes a first transfer device 42 that transfers the disc-shaped substrate 12 manufactured by the substrate manufacturing device 60 from the terminal 38 of the pre-process transfer line to the inspection table 40. And a second transfer device 48 for selectively distributing the disc-shaped substrate 12 after the inspection from the inspection table 40 to the post-process transfer line 44 or the discharge line 46. The post-process transfer line 44 converts the disc-shaped substrate 12 that has passed the inspection into a reflective film 14A, a heat-resistant protective film 14B, a recording film 14C, an interface layer 14D, a heat-resistant protective film 14E, a light transmission layer 14F, and a hard coat layer 14G. Is transported to a film forming line 70 for forming a film.

  Next, referring to FIG. 9, a process of detecting a surface defect or an internal defect of the disc-shaped substrate 12 conveyed from the substrate manufacturing apparatus 60 by the defect detection device 10 and completing the optical disc 14 is described. explain.

  The disk-shaped substrate 12 is continuously manufactured by the substrate manufacturing apparatus 60, and the manufactured disk-shaped substrate 12 is placed on the inspection table 40 from the transport terminal 38 by the first transfer device 42 with the surface 12 </ b> A facing upward. It is transferred onto the upper rotation support device 16.

  Next, irradiation light is projected from the irradiation device 18 onto the upper surface 12A of the disk-shaped substrate 12 to be inspected while rotating the motor 26 at a predetermined rotation speed via the motor control device 28. The reflected light is input to each pixel of the line camera 20. At this time, the line camera 20 measures the light amount in one photographing (one scan) and scans continuously. At this time, the disc-shaped substrate 12 rotates, and the positions where the light enters and reflects are sequentially shifted, so that the reflected light is received at sequentially shifted times.

  At this time, the incident light I, which is the irradiation light, is refracted from the front surface 12A of the disc-shaped substrate 12, reaches the back surface 12B, is reflected here, and is emitted from the front surface 12A as reflected light R, as shown in FIG. .

  If there is a defect on the optical path of the incident light I or the reflected light R, the amount of reflected light at that portion decreases (or increases). The amount of light received by the pixel falls below the low threshold level (or exceeds the high threshold level) as shown in FIG.

Therefore, this is the defect detection in step 101 of FIG. If there is a defect detected at step 101, in a next step 102, for example, the size of the abnormal portion D ₁ as shown in FIG. 7 as three dots in the shape of a disc substrate radially, of four dots in the scanning direction Measured.

  When there is a defect F on the surface 12A of the disc-shaped substrate 12, the defect F crosses the optical path of the incident light I as shown in FIG. After the time, the defect F crosses the optical path of the reflected light R as shown in FIG.

Therefore, as shown in FIG. 7, the defect F is located at the same position in the radial direction of the disk-shaped substrate 12 and is shifted in the scanning direction, so that the abnormal portion D ₁ (real image) and the abnormal portion D ₂ (shadow) Is detected by the image processing device 22.

  When the defect G is present in the cross section of the disc-shaped substrate 12, as shown in FIGS. 11A and 11B, the optical path of the incident light I and the disc-shaped reflection light R in the cross-section of the disc-shaped substrate 12. The optical path sequentially crosses the cross section of the substrate 12. Also in this case, the real image and the shadow are detected as being shifted.

Next, in step 103, it is determined whether or not the two detected abnormal portions D ₁ and D ₂ are similar, that is, whether or not there is a relationship between the real image and the shadow, and the distance L between the two is determined. (See FIG. 7).

If the similar shape is recognized, the process proceeds to the next step 104, and the CPU 24 determines whether or not the distance between the _two abnormal portions D ₁ and D ₂ is substantially equal to the set value L or smaller than the set value. Is determined.

  Here, as shown in FIG. 12, when the defect G is within the cross section of the disc-shaped substrate 12, the abnormal position between the detection position on the optical path of the incident light I and the detection position on the optical path of the reflected light is detected. Is naturally smaller than the set value L (mm).

  Accordingly, when two detected abnormal portions are similar in shape, when the distance between the two is substantially equal to L, the abnormal portion indicates a surface defect, and when smaller than L, indicates an internal defect. Is determined.

As a result of the determination, if the distance between the _two abnormal portions D ₁ and D ₂ is substantially equal to the set value L, it is determined that the surface defect is present (Step 105), and the process proceeds to Steps 106 and 107.

  In step 106, the CPU 24 determines the size of a surface defect (an abnormal portion formed of an aggregate of dark spots or bright spots) by comparing the size with a preset input value.

  If the size is equal to or smaller than the set value, it is a small defect, the result is OK in step 107, and the disk-shaped substrate 12 on the inspection table 40 is transferred to the post-process transfer line 44 by the second transfer device 48. You.

  If the size is equal to or larger than the set value, this is determined as NG in step 109, and the second transfer device 48 transfers the disc-shaped substrate 12 on the inspection table 40 to the discharge line 46.

  In step 107, when the surface defects are small but clumped, they are regarded as one large defect, that is, a set determination is performed.

  In this set determination, it is determined whether or not this exceeds a set value, for example, by a ratio of the number of dots (individual abnormal points) within a certain range of the area in FIG.

  If the value is equal to or less than the set value, the result is OK in step 110, the disc-shaped substrate 12 is sent to the film forming line 70, and the recording film 14C, the light transmitting layer 14F and the like are formed (see step 120). If the value is equal to or larger than the set value, the defect is a large defect. In step 111, the result is NG, and the disc-shaped substrate 12 is transferred to the discharge line 46.

  If the defect detected in the above-mentioned step 103 is not a similar shape, and if the distance between the two is less than or equal to the set value, the defect is determined to be an internal defect in step 112, and the next step 113 and step Proceed to 114.

  In step 113, it is determined whether or not the size of the internal defect is larger than a set value. If the size is smaller than the set value, it is OK. In step 115, the disc-shaped substrate 12 on the inspection table 40 is 44, the reflection film 14A, the heat-resistant protective film 14B, the recording film 14C, the interface layer 14D, the heat-resistant protective film 14E, the light transmitting layer 14F, and the hard coat layer 14G are formed in the film forming line 60 in Step 120. The optical disk 14 is completed.

  If the value is equal to or larger than the set value, the process proceeds to step 116 to issue a warning, but the disc-shaped substrate 12 on the inspection table 40 is sent to the post-process transfer line 44. However, in this case, in step 117, a large number of small internal defects are generated, and the fact that a large internal defect has been generated is fed back to the production process.

  In step 114, as in step 107, the set is determined. As a result, if the set of small abnormal parts is equal to or smaller than the set value, the process proceeds to step 118 and the determination is OK. From step 40, it is transferred to the post-process transfer line 44, and becomes a completed product via the film forming line 70 in step 121 as described above.

  If the value is equal to or greater than the set value, the process proceeds to step 116, where a warning and feedback to the production process in step 117 are issued.

  Here, the wavelength of the emitted light (irradiation light) from the λ / 4 phase difference plate 18E in the irradiation device 18 is changed to 600-700 nm wavelength light by transmitting through the bandpass filter 18B and the SC filter 18C. However, this is based on the spectral characteristics of the reflectance of the disc-shaped substrate 12 made of PC, and the wavelength is set in the region where the reflectance is the lowest. By doing so, the transmittance in the disk-shaped substrate 12 is maximized, and the contrast with an abnormal part when a defect is present is emphasized. The wavelength can be selected in a wavelength range that can be received by the line camera 20 depending on the type of the light transmitting material, and any wavelength among visible light, near ultraviolet light, or near infrared light (350 to 1100 nm) can be selected. Is emphasized, so that 600 to 700 nm is preferable.

  As described above, the irradiation device 18 uses the linear polarizer 18D and the λ / 4 phase difference plate 18E to irradiate the disc-shaped substrate 12 with right-handed or left-handed circularly-polarized light. The circularly polarizing plate 20A is also provided on the incident optical axis of, so that the circularly polarized light from the irradiation device 18 is reflected, and only the circularly polarized light whose turning direction is reversed is incident on the line camera 20. .

  This is to prevent the surrounding noise light from being incident on the line camera 20 and to enhance the contrast between the portion having no abnormal portion and the abnormal portion.

  Therefore, if the contrast between the abnormal part and the other part in the reflected light received by the line camera 20 is sufficient, it is not necessary to limit the wavelength of the irradiating light to a specific region or to use circularly polarized light.

  Further, in the example of the above-described embodiment, the line camera 20 is configured by arranging a plurality of pixels, for example, pixel numbers 1 to 4096, linearly in the radial direction from the inner peripheral side to the outer peripheral side of the disc-shaped substrate 12. However, in the rotation direction of the disc-shaped substrate 12, the distance that each pixel scans in a unit time is shorter in the radial direction inside, that is, smaller as the pixel No. is smaller, and larger in the radial direction outside, that is, larger as the pixel No. is larger. A difference occurs in the number of detected dots. For example, as shown in Table 1, it is preferable that the scanning distance of each pixel per unit time is weighted so that the size of all pixels is substantially the same.

  Furthermore, the present invention is applied to a case where a photodetector other than a line camera is used. For example, one or several light receivers in a line camera may be scanned in the radial direction while rotating the disk-shaped substrate.

  Also, as the disk-shaped substrate 12 is made of PC and the whole is formed of a light-transmitting material, the present invention reflects the light-transmitting light so that the incident light is reflected on the back surface of the disk-shaped substrate and the reflected light can be detected. Applied to a disc-shaped substrate.

  In addition, the measurement can be performed in a rotation direction opposite to the rotation direction of the disc-shaped substrate in FIG. 3. In this case, the defect is first detected by the reflected light R (real image), and then detected by the irradiation light I (shadow). ) Is done.

  The disc-shaped substrate 12 that has passed the above inspection is subjected to the reflection film 14A, the heat-resistant protective film 14B, the recording film 14C, the interface layer 14D, the heat-resistant protective film 14E, the light transmitting layer 14F, and the hard coat layer 14G in the film forming line 70. Is formed on the optical disk 14, but the present invention is not limited to this, and is applied to a method of manufacturing an optical disk on which at least a recording film and a light transmitting layer are formed.

The disc-shaped substrate 12 is made of polycarbonate (refractive index n = 1.58) having a thickness of t = 1.1 mm, the incident angle θ ₂ = 45 °, and irradiation light (circularly polarized light) having a wavelength of 650 nm is applied to the surface of the disc-shaped substrate 12. 12A, and the reflected light was received by a 4096 pixel line camera.

In this case, since n = Sin θ ₂ / Sin θ ₁ = 1.58, θ ₁ = 26.5 °, L = 2t Tan θ ₁ = 1.1 mm, and when L = 1.1 mm, a surface defect, 0 ≦ When L <1.1 mm, internal defects occur.

  It is desirable to remove the internal defect existing on the extreme surface because there is a possibility that the surface is uneven, and it is also desirable to remove the internal defect even when the distance is L ± α in consideration of measurement error. . α can be set to, for example, 5%. If the measurement result is> L + α, it is determined that the real image and the shadow are not the same defect.

  In the actual determination, in consideration of the above-described error and the like, as an example of a surface defect where 1.05 ≦ L ≦ 1.15 is a surface defect and 0 ≦ L <1.05 is an internal defect, a disk-shaped oil-based ink is used. A defect having a size of about 0.6 mm is formed on the surface of the substrate, and another disk-shaped substrate is formed by marking the surface of the rear surface 12B of the disk-shaped substrate 12 with oil-based ink as an example of an internal defect. , And a defect having a defect in the light-transmitting material layer was selected, and the defect was measured by the configuration as shown in FIG. 1. As shown in Table 2, the surface defect and the internal defect and the back surface of the disc-shaped substrate were measured. The defect L clearly differs in the distance L between the real image and the shadow, and the surface defect and the internal defect can be distinguished.

In Table 2,
Defect radius position R: Displays the radial position of the detected defect. Defect radial direction: Displays the number of detected dots in the radial direction of the detected defect. Defect circumferential direction: Displays the number of detected dots in the circumferential direction of the detected defect. Scan S: The number of scans between the real image and the shadow is displayed. Real image / shadow distance L: The radial position of the defect and the number of scans between the real image and the shadow
L (mm) = [R × 2 × π / 24000 (the number of scans per disk rotation)] × S
Defect type: defect type determined by L (mm) Defect disk No. 1-3 is determined as a “surface” defect because 1.05 ≦ L ≦ 1.15 (α is set to 0.05; 1.15 <is not the same defect).
Defective disk No. 4-6, L (mm) = 0 (no shadow) is a defect on the back surface of the disc-shaped substrate, and is determined as an “internal” defect. 7-9 is judged as “internal” defect because L (mm) <1.1,
And

FIG. 1 is a block diagram showing a defect detection device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an enlarged part of a state in which a reflective film, a recording film, and the like are formed on a disc-shaped substrate as an object by the defect detection device and method according to the present invention. FIG. 2 is a perspective view showing a relationship between an irradiation device, a line camera, and a disk-shaped substrate in the defect detection device of FIG. FIG. 2 is a schematic cross-sectional view showing an optical system of irradiation light and reflected light of the irradiation device and the line camera. Optical path diagram showing the state of incident light and reflected light when light enters the disk-shaped substrate in an enlarged manner. FIG. 4 is a diagram showing the state of the amount of reflected light at each pixel in a line camera of the defect detection device. Diagram showing defects detected in the image processing device of the defect detection device on a map FIG. 2 is a schematic plan view including a partial block diagram showing a method of manufacturing an optical disc including a transport device for loading and unloading a disc-shaped substrate as an object to and from the defect detection device; The flowchart which shows the process which performs the defect detection of a disk-shaped board | substrate by the said defect detection apparatus. An optical path diagram showing a process of detecting a defect on the surface of a disk-shaped substrate made of a light-transmitting material by the defect detection device. An optical path diagram showing a process of detecting a defect in a cross section of a disk-shaped substrate made of a light-transmitting material by the defect detection device. Optical path diagram showing the relationship between the position on the defect incident optical path and the position on the reflected optical path when there is a defect in the cross section of the disc-shaped substrate made of a light transmitting material

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 10 ... Defect detection device 12 ... Disc-shaped substrate 12A ... Front surface 12B ... Back surface 14 ... Optical disk 14C ... Recording film 14F ... Light transmission layer 16 ... Rotation support device 18 ... Irradiation device 18A ... Light source 18B ... Bandpass filter 18C ... SC filter 18D ... Linear polarizing plate 18E ... λ / 4 phase difference polarizing plate 20 ... Line camera 20A ... Circular polarizing plate 22 ... Image processing device 24 ... CPU
34 ... Conveying device 40 ... Inspection table 42 ... First transfer device 48 ... Second transfer device 50 ... Optical disk manufacturing device 60 ... Substrate manufacturing device 70 ... Film forming line I ... Irradiation light R ... Reflection light

Claims (18)

  While rotating a disc-shaped substrate made of a light-transmitting material, the process of irradiating irradiation light on the surface of the disc-shaped substrate obliquely in one of the rotation directions with respect to a perpendicular to the surface, and entering the disc-shaped substrate from the surface When the reflected light on the back side of the irradiation light is received with a time lag sequentially from a direction inclined to the side opposite to the irradiation light with respect to the perpendicular, and the received reflected light amount is smaller or larger than a set value. And determining whether or not the two abnormal portions have similar shapes when the two abnormal portions have a similar shape, and determining whether the two abnormal portions have a similar shape. Measuring the distance in the rotational direction of the disc-shaped substrate by image processing, determining whether the distance is a set value, and determining that there is a surface defect when the distance is the set value. And a disc-shaped substrate comprising Defect detection method.   While rotating a disc-shaped substrate made of a light-transmitting material, the process of irradiating irradiation light on the surface of the disc-shaped substrate obliquely in one of the rotation directions with respect to a perpendicular to the surface, and entering the disc-shaped substrate from the surface When the reflected light on the back side of the irradiation light is received with a time lag sequentially from a direction inclined to the side opposite to the irradiation light with respect to the perpendicular, and the received reflected light amount is smaller or larger than a set value. And determining whether or not the two abnormal portions have similar shapes when the two abnormal portions have a similar shape, and determining whether the two abnormal portions have a similar shape. Measuring the distance in the rotational direction of the disc-shaped substrate by image processing to measure the position of the defect in the disc-shaped substrate in the thickness direction. In claim 1 or 2,
The process of determining the abnormal portion is a process of detecting an abnormal point that occurs when the amount of reflected light received is smaller or larger than a set value, and displaying the abnormal point on a map corresponding to a position on the surface of the disk-shaped substrate. Determining whether or not the displayed set of abnormal points has a shape as an abnormal part. In claim 1, 2 or 3,
The reflected light is received by a line camera in which a number of pixels are arranged in the radial direction of the disc-shaped substrate from the center to the outer periphery of the disc-shaped substrate, and the information captured by the line camera is image-processed to produce the two abnormalities. A method for detecting a defect in a disk-shaped substrate, comprising measuring a distance between parts. In any one of claims 1 to 4,
The set value L (mm) serving as a criterion for determining the distance between the two abnormal portions is such that the refractive index of the light transmitting material is n, the thickness is t (mm), and the irradiation light is applied to the surface of the disc-shaped substrate. when the incident angle _{θ 2, n = Sinθ 2 /} Sinθ 1, a defect detection method of a disk-shaped substrate, characterized in that the L = 2tTanθ _1. In any one of claims 1 to 5,
A defect detection method for a disc-shaped substrate, wherein the wavelength of the irradiation light is 600 to 700 nm. In any one of claims 1 to 6,
A defect detection method for a disc-shaped substrate, wherein an incident angle of the irradiation light with respect to a normal to a surface of the light transmitting material layer is set to 15 ° to 85 °, preferably 30 ° to 45 °.   A disk-shaped substrate formed of a light-transmitting material is placed thereon, and a rotation support device for rotating the disk-shaped substrate, and the surface of the disk-shaped substrate is inclined in one of rotation directions with respect to a perpendicular to the surface. Irradiation device for irradiating irradiation light, and simultaneously or sequentially measuring in the radial direction from the center to the outer periphery of the disk-shaped substrate while rotating the disk-shaped substrate, the irradiation light is from the surface of the disk-shaped substrate to the inside Incident, and a light detection device that sequentially receives the reflected light generated on its back surface with a time delay, and when the reflected light amount received by the light detection device is smaller or larger than a set value, it is determined as an abnormal portion, When there is at least two abnormal portions with a time lag, it is determined whether or not these abnormal portions have a similar shape. In the case of a similar shape, the distance between the two abnormal portions in the disk-shaped substrate rotation direction is determined. Image to measure Processing unit and located surface defects and determining device and a disk-shaped substrate defect detection apparatus comprising a when the distances the measured value. In claim 8,
The image processing apparatus detects an abnormal point when the amount of reflected light received by the photodetector is smaller or larger than a set value, and displays the abnormal point on a map corresponding to a position on the surface of the disk-shaped substrate. A defect detection apparatus for a disc-shaped substrate, wherein it is determined whether or not a set of displayed abnormal points has a shape as an abnormal portion. In claim 8 or 9,
The said light detection apparatus is a line camera which arranges many pixels in the radial direction of a disk-shaped substrate from the center of the said disk-shaped substrate to an outer periphery, The defect detection apparatus of a disk-shaped substrate characterized by the above-mentioned. In claim 8, 9 or 10,
In the determination apparatus, the set value L (mm) serving as a criterion for determining the distance between the two abnormal portions is such that the refractive index of the light transmitting material is n, the thickness is t (mm), and the disk of the irradiation light is the incident angle to Jo substrate surface is taken as _{θ 2, n = Sinθ 2 /} Sinθ 1, the defect detection apparatus of a disk-shaped substrate, characterized in that it is set so that L = 2tTanθ _1. In any one of claims 8 to 11,
A defect of the disc-shaped substrate, wherein a band-pass filter that transmits only light in a wavelength region of a predetermined width centered on a specific wavelength is provided on an optical path of irradiation light from the irradiation device to the disc-shaped substrate. Detection device. In claim 12,
A polarizing plate for polarizing the light transmitted through the band-pass filter to one of left-handed or right-handed circularly polarized light and two linearly polarized lights whose polarization planes are orthogonal to each other is provided, and the light detection device is provided from the disc-shaped substrate. Wherein a light-receiving-side polarizing plate that transmits only the polarized light whose phase is shifted by π with respect to the polarized light passing through the polarizing plate is provided in the reflected light path to the disk-shaped substrate. . A process of continuously forming a disc-shaped substrate from a light-transmitting material, and a process of rotating the disc-shaped substrate and injecting irradiation light to a surface thereof while being inclined in one of rotation directions with respect to a perpendicular to the surface. And, the irradiation light incident on the disc-shaped substrate from the front surface, the reflected light on the back surface, from the direction inclined to the opposite side to the irradiation light with respect to the perpendicular, received the light sequentially and staggered, received When the amount of reflected light is smaller or larger than a set value, the process is determined as an abnormal portion, and when there are two abnormal portions with a time lag, it is determined whether or not these two abnormal portions have similar shapes. Measuring the distance in the rotational direction of the disc-shaped substrate between these two abnormal portions when they are similar to each other by image processing; determining whether the distance is a set value; Is set value, it is judged that there is a surface defect. The method comprising, a disc-shaped substrate other than where it is determined that there is the surface defects, the process of forming at least a recording layer and a light transmission layer in this order,
A method for manufacturing an optical disk, comprising: A process of continuously forming a disc-shaped substrate from a light-transmitting material, and a process of rotating the disc-shaped substrate and injecting irradiation light to a surface thereof while being inclined in one of rotation directions with respect to a perpendicular to the surface. And, the irradiation light incident on the disc-shaped substrate from the front surface, the reflected light on the back surface, from the direction inclined to the opposite side to the irradiation light with respect to the perpendicular, received the light sequentially and staggered, received When the amount of reflected light is smaller or larger than a set value, the process is determined as an abnormal portion, and when there are two abnormal portions with a time lag, it is determined whether or not these two abnormal portions have similar shapes. Measuring the distance between these two abnormal portions when they have similar shapes in the direction of rotation of the disk-shaped substrate by image processing to measure the position of the defect in the disk-shaped substrate in the thickness direction; Disc shape other than surface defects A plate, a step of forming at least a recording layer and a light transmission layer in this order,
A method for manufacturing an optical disk, comprising: In claim 14 or 15,
The process of determining the abnormal portion is a process of detecting an abnormal point that occurs when the amount of reflected light received is smaller or larger than a set value, and displaying the abnormal point on a map corresponding to a position on the surface of the disk-shaped substrate. Determining whether or not the displayed set of abnormal points has a shape as an abnormal portion. In any one of claims 14 to 16,
The reflected light is received by a line camera in which a large number of pixels are arranged in the radial direction of the disc-shaped substrate from the center to the outer periphery of the disc-shaped substrate, and information captured by the line camera is image-processed to perform the two abnormalities. A method for manufacturing an optical disc, comprising measuring a distance between the sections. In any one of claims 14 to 17,
The set value L (mm) serving as a criterion for determining the distance between the two abnormal portions is such that the refractive index of the light transmitting material is n, the thickness is t (mm), and the irradiation light is applied to the surface of the disc-shaped substrate. when the incident angle _{θ 2, n = Sinθ 2 /} Sinθ 1, optical disc manufacturing method is characterized in that the L = 2tTanθ _1.

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