JP5255342B2 - Defect detection device for light transmissive film - Google Patents

Description

  The present invention is a light transmissive film used for the purposes of antireflection, scattering prevention, heat ray prevention (blocking), heat insulation, antifouling, durability (protection), etc. in applications such as optical applications, architectural applications, and automotive applications. The present invention relates to an apparatus for detecting a defect in a (light-transmitting film).

  Examples of the light transmissive film A used for optical applications, architectural applications, in-vehicle applications, and the like include, for example, a light characteristic control film for controlling light reflection characteristics and absorption characteristics on the base film 8. Or what formed by laminating | stacking the some coating layer 9 is mentioned. Such a light transmissive film A is used as an antireflection filter on the surface of a display such as a plasma display or a liquid crystal display.

  In detecting the defect of the light-transmitting film A provided with such a coating layer 9, a defect (defect having a nucleus) that is caused by a foreign substance entering between the base film 8 and the coating layer 9 can be detected visually. . However, as shown in FIG. 4, the coating layer 9 has a variation in thickness, which causes defects (nuclear-free defects) in which portions slightly different from the surrounding color are detected by visual inspection. In inspection, about 90% of defects may be missed.

  Therefore, conventionally, as disclosed in Patent Document 1, the light reflected on the front and back surfaces of the coating layer 9 formed on the light transmissive film A is compared with the light transmissive film A located on the surface of the guide roll. It has been proposed to detect defects by performing illumination so as to interfere and imaging the interference pattern. In this case, not only defects with nuclei but also defects without nuclei are detected.

  As shown in FIG. 4, the interference pattern due to the film thickness unevenness causes interference due to an optical path difference between the reflected light L <b> 1 on the front surface side of the coating layer 9 and the reflected light L <b> 2 on the back surface side of the coating layer 9. When the light of a specific wavelength region intensifies and the light of other wavelengths weakens, when the difference in film thickness occurs, the light of different wavelengths strengthens accordingly.

However, when the above interference pattern is picked up by the image pickup means, there is a problem that a high resolution is required for the image pickup unit, resulting in a complicated device configuration and a high equipment investment.
JP 2006-208196 A

  The present invention has been made in view of the above problems, and it is possible to detect defects due to uneven thickness of a coating layer in a light-transmitting film in which a coating layer is provided on one side of a base film with a simple configuration and high accuracy. It is an object of the present invention to provide a defect detection device for a light transmissive film that can be performed.

The present invention is a defect detection apparatus for detecting a defect in a light transmissive film A provided with a coating layer 9 on one surface side of a base film 8, and includes a conveying means 5 for conveying the light transmissive film A, A plurality of illumination means 6 for irradiating light to the light transmissive film A from one surface side, receiving light of a specific wavelength range irradiated from the plurality of illumination means 6 and reflected on one surface side of the light transmissive film A A plurality of imaging units 1 for imaging, and detection means 3 for detecting a defect of the light transmissive film A from an image obtained by imaging by the imaging unit 1 are provided. Each illumination unit 6 constituting the plurality of illumination units 6 and each imaging unit 1 constituting the plurality of imaging units 1 are provided along a transported path. Each imaging unit 1 of the plurality of imaging units 1 is provided corresponding to each illumination unit 6 of the plurality of illumination units 6 with different specific wavelength ranges for receiving light.

  For this reason, when the coating layer 9 has defects in film thickness unevenness and the light in the specific wavelength region is intensified by interference between the light reflected on the front surface side and the light reflected on the back surface side, the specific wavelength The defect can be detected by detecting the area with the imaging unit 1, and at least one of the specific wavelength range for receiving each of the imaging units 1 and the reflection angle of the received light from the light-transmitting film A is By being different, a different film thickness of the coating layer 9 is detected for each image pickup unit 1, and the resolution required for the image pickup unit 1 is reduced to simplify the apparatus configuration, and the film thickness unevenness in a wide range. Defects can be detected.

  In the present invention, it is also preferable that the imaging unit 1 includes a wavelength filter that transmits light in a specific wavelength range.

  In this case, it is possible to detect only light in a specific wavelength range by the imaging unit 1 with a simple configuration, thereby further simplifying the apparatus.

  In the present invention, the observation is performed on the other surface side of the light transmissive film A imaged by the imaging unit 1 and subjected to a reflectance reduction process for reducing the reflectance of light in a specific wavelength region. It is also preferable to provide the auxiliary member 2 for use.

  In this case, the observation auxiliary member 2 supports the light transmissive film A at the time of imaging, so that generation of wrinkles in the light transmissive film A is prevented, and between the imaging unit 1 and the light transmissive film A. Positioning is performed to prevent out-of-focus. Moreover, the ratio of the reflected light from the observation auxiliary member 2 in the light in the specific wavelength range received by the imaging unit 1 is reduced, and the intensity change of the reflected light due to the defect of the light transmissive film A becomes clear. . For this reason, it is possible to reduce the reflected light from the observation auxiliary member 2 while increasing the amount of light emitted from the illuminating means 6, which is caused by a defect in the coating layer 9 in the image captured by the imaging unit 1. Thus, the defect detection accuracy can be improved by clarifying the intensity change of the reflected light.

  Moreover, in this invention, the auxiliary member 2 for observation distribute | arranged to the other surface side of the said light transmissive film A imaged by the said imaging part 1, the other surface of the said light transmissive film A, and the said auxiliary member for observation 2 and a filling means for bringing the light-transmissive film A and the observation auxiliary member 2 into close contact with each other by interposing a filler 4 between the filler 4 and the filler 4 for light in a specific wavelength range. It is also preferable that it absorbs.

  In this case, the filler 4 absorbs light in the specific wavelength region, whereby reflected light in the specific wavelength region from the observation auxiliary member 2 can be reduced. Further, the filler 4 is captured during imaging by the imaging unit 1. By adhering the light transmissive film A to the surface of the observation auxiliary member 2, the air between the other surface A2 of the light transmission film A on the observation auxiliary member 2 side and the observation auxiliary member 2 is excluded, Reflected light from the other surface A2 on the observation auxiliary member 2 side of the light transmissive film A can be suppressed, and the detection accuracy of defects can be increased by reducing the presence of unnecessary reflected light when detecting defects. .

In the present invention, since the specific wavelength ranges received by the plurality of imaging units are different from each other, it is possible to detect a defect due to the uneven thickness of the coating layer in the light transmissive film with a simple configuration and high accuracy.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The defect detection apparatus according to the present embodiment shown in FIG. 1 is used in applications such as optical applications, architectural applications, and in-vehicle applications, such as antireflection, scattering prevention, heat ray prevention (blocking), heat insulation, antifouling, and durability improvement (protection). It is used to detect defects in a light transmissive film (film having light transmissive property) A used for the purpose such as). As this light transmissive film A, for example, a colorless and transparent base film 8 such as a polyester film such as a polyethylene terephthalate film is provided by laminating a coating layer 9 for controlling light reflection characteristics and absorption characteristics. Can be mentioned. Examples of such light transmissive film A include, but are not limited to, an antireflection film (AR film) for displays such as liquid crystal displays, night vision films for automobiles, and other general optical control films. .

  When the light-transmitting film A is manufactured, as shown in FIG. 4, the coating agent 9 is unevenly applied due to contamination (contamination) on the surface of the base film 8, repelling due to adhesion of foreign matters, and the like. Uneven thickness defects may occur. The defect detection apparatus according to the present embodiment is preferably used for detecting such defects.

  As shown in FIG. 1, the defect detection apparatus includes a conveyance unit 5, an imaging unit 1, an observation auxiliary member 2, an illumination unit 6, a detection unit 3, and the like.

  The conveyance means 5 is provided in order to convey the elongate strip | belt-shaped (sheet-like) light-transmitting film A continuously at a fixed speed. The conveying means 5 includes, for example, a feeding drum 12 in which the light transmissive film A is wound in a roll shape, a driving means 13 such as a motor for rotating the drum 12 to sequentially feed the light transmissive film A, and after defect detection And a winding drum 14 for winding the light-transmitting film A.

  The illumination means 6 is provided to irradiate the light transmissive film A with light from the one surface A1 side.

  The imaging unit 1 is provided to receive and image the reflected light of the light emitted from the illumination unit 6 from the one surface A1 (front surface) side of the light transmissive film A. As the imaging unit 1, for example, a line camera that is formed by a CCD camera or the like and captures the entire appearance of the light transmissive film A is used.

  The detection means 3 is provided for detecting a defect of the light transmissive film A from the image obtained by the imaging unit 1. The detecting means 3 is constituted by a general-purpose computer equipped with a display, for example. The detection means 3 performs, for example, a calculation process on an image obtained by the imaging unit 1 by image processing that is generally performed widely, or is visually confirmed by a person, so that the light transmissive film A is detected. What can analyze and detect a defect is used.

  The observation auxiliary member 2 is disposed on the other surface A2 (back surface) side of the light transmissive film A during imaging by the imaging unit 1. The observation auxiliary member 2 supports the light transmissive film A during imaging, so that wrinkles are prevented from occurring in the light transmissive film A, and the imaging unit 1 and the light transmissive film A are positioned. This prevents the occurrence of out-of-focus. The observation auxiliary member 2 is composed of a roll that rotates while contacting the other surface A2 of the light transmissive film A.

  The defect detection process of the light transmissive film A using the defect inspection apparatus according to this embodiment will be described.

  First, by rotating the feeding drum 12 by the driving means 13, the light transmissive film A wound around the drum 12 is sequentially fed and conveyed to the winding drum 14 at a constant speed. The light transmissive film A is conveyed between the feeding drum 12 and the take-up drum 14 while being in contact with the surface (outer surface) of the observation auxiliary member 2. Although the conveyance speed of the light transmissive film A is suitably set according to the capability of the imaging part 1 or the conveyance means 5, etc., it can be set to 5-3000 m / min, for example.

  In this way, the illumination means 6 irradiates light on the surface of the light transmissive film A being transported on which the coating layer 9 is formed, and the imaging unit 1 receives the reflected light from the light transmissive film A. And take an image.

  Next, an image of one surface A1 of the light transmissive film A imaged by the imaging unit 1 is taken into the detection means 3, and a defect is detected based on the image. At this time, the entire defect of the light transmissive film A can be detected by conveying the light transmissive film A over the entire length.

  In such a defect inspection apparatus, the imaging unit 1 receives and detects light in a specific wavelength range. In order for the imaging unit 1 to receive and detect light in a specific wavelength range, for example, an illumination unit 6 that emits only light in the specific wavelength range is used, or the imaging unit 1 uses light in the specific wavelength range. Those that sense only are used.

  As the illumination unit 6 that irradiates only light in a specific wavelength range, for example, an illumination unit 6 configured by a combination of an illumination tool 6a as illustrated in FIG. 1 and a color filter 6b that transmits only light in a specific wavelength range. And illumination means 6 composed of a colored illumination lamp that emits light in a specific wavelength region such as red. Thus, when the illumination means 6 which irradiates only the light of a specific wavelength range is provided, what senses the light of the wavelength range including the said specific wavelength range at least as the imaging part 1 is provided.

  Examples of the imaging unit 1 that senses only light in a specific wavelength range include an imaging unit 1 that includes a wavelength filter that allows only light in a specific wavelength range to pass through. When the imaging unit 1 that senses only light in a specific wavelength range is provided as described above, an illumination unit 6 that emits light in a wavelength range including at least the specific wavelength range is provided.

  As described above, when the imaging unit 1 receives and detects light in a specific wavelength region, when the coating layer 9 is uneven in film thickness and the light in the specific wavelength region in the reflected light is strengthened, the light in this specific wavelength region is detected. Defects are detected based on the intensity of.

  By the way, when the reflected light L1 on the front surface side of the coating layer 9 and the reflected light L2 on the back surface side of the coating layer 9 interfere with each other, light of a specific wavelength intensifies and light of other wavelengths weakens. For this reason, it is detected that the coating layer 9 has a film thickness corresponding to the specific wavelength region by detecting the improvement in the intensity of light in the specific wavelength region by the imaging unit 1. At this time, if the reflection angles of the light are the same as shown in FIG. 4A, the wavelength of the light strengthened by the interference of the reflected lights L1 and L2 changes due to the change in the film thickness of the coating layer 9. . On the other hand, if the wavelength of the light is the same, the reflection angle of the light strengthened by the interference of the reflected light L1 and L2 changes as shown in FIG.

  For this reason, in the present invention, as each imaging unit 1, each imaging unit 1 is provided by providing a plurality of imaging units having at least one of a specific wavelength range to receive light and a reflection angle of the received light from the light-transmitting film. Each time a different film thickness of the coating layer 9 is detected, a change in the film thickness of the coating layer 9 is detected over a wide range.

  In the present embodiment shown in FIG. 1, as the imaging unit 1, a plurality of imaging units 1 that receive and capture light in different specific wavelength ranges are provided. The plurality of imaging units 1 are provided in combination with a plurality of illumination means 6 corresponding to each imaging unit 1. That is, as shown in FIG. 1, along the path along which the light transmissive film A is conveyed, the illumination unit 6, the imaging unit 1 that receives and captures reflected light of the light emitted from the illumination unit 6, and A plurality of combinations of the auxiliary observation members 2 are provided, and as the light transmissive film A is conveyed, light in different specific wavelength ranges is sequentially received by each imaging unit 1 and imaged. Each of the plurality of imaging units 1 is provided so as to detect reflected light emitted from the light transmissive film A at the same angle. In this case, when the film thickness of the coating layer 9 changes, the wavelength range of the intensifying light in the reflected light changes, and this intensifying light is detected by one of the imaging units 1, so that the film of the coating layer 9 A change in thickness is detected.

  In the other embodiment shown in FIG. 2, a plurality of imaging units 1 that receive and image light in the same specific wavelength range are provided as the imaging unit 1. The plurality of imaging units 1 are provided in combination with one illumination unit 6 and one auxiliary auxiliary member 2 for observation, and each imaging unit 1 has a different reflected light of light emitted from the illumination unit 6. It is provided to receive light at a reflection angle. In this case, when the film thickness of the coating layer 9 changes, the reflection angle of light having a specific wavelength that strengthens in the reflected light changes, and this strengthening light is detected by any one of the imaging units 1, whereby the coating layer 9 changes in film thickness are detected.

  In each of the above embodiments, one of the specific wavelength range received by the imaging unit 1 and the reflection angle of the received light from the light-transmitting film is fixed and the other is different. If different film thicknesses are detected in 1, both the specific wavelength range for receiving light and the reflection angle of the received light from the light-transmitting film may be different between the plurality of imaging units 1.

  The detection unit 3 can create map data that identifies the position of the defect from the imaging result of each imaging unit 1.

  In addition, the observation auxiliary member 2 may be subjected to a reflectance reduction process for reducing the reflectance of light in the specific wavelength region in the observation auxiliary member 2. In this case, the ratio of the reflected light from the observation auxiliary member 2 in the light in the specific wavelength range received by the imaging unit 1 is reduced, and the intensity of the reflected light in the specific wavelength range due to the defect of the light transmissive film A Change becomes clear. In this case, the reflected light from the observation auxiliary member 2 can be reduced while increasing the amount of light emitted from the illuminator 6, and defects in the coating layer 9 in the image captured by the imaging unit 1 can be reduced. It is possible to improve the defect detection accuracy by clarifying the intensity change of the reflected light caused thereby.

  As a reflectance reduction process, the roughening process which roughens the surface of the auxiliary member 2 for observation is mentioned, for example. In this case, the reflected light from the observation auxiliary member 2 is scattered by the roughening, so that the reflected light from the observation auxiliary member 2 detected by the imaging unit 1 is reduced. When the surface of the observation auxiliary member 2 is roughened in this way, reflected light of light in a wide wavelength range is reduced, so that reflected light in various specific wavelength ranges can be reduced. As a roughening method, an appropriate method such as polishing or sandblasting is selected. The surface roughness of the observation auxiliary member 2 after the roughening treatment is appropriately adjusted so that the reflectance of light is sufficiently reduced, but the centerline average roughness (Ra; JIS B0601: 1982) is particularly high. If it is 0.4 μm or more, the reflected light from the observation auxiliary member 2 is sufficiently reduced. However, if the unevenness of the unevenness on the surface of the auxiliary member for observation 2 becomes too large, the unevenness may be detected by the imaging unit 1 or the light transmissive film A may be scratched by the unevenness. In order to prevent such a problem, the ten-point average roughness (Rz; JIS B0601: 1982) of the surface of the auxiliary member for observation 2 is less than 20 μm and the maximum height (Rmax; JIS B0601: 1982) is Desirably, it is less than 40 μm.

  When the observation auxiliary member 2 is subjected to the surface roughening treatment, the defect detection device excludes the air between the light transmissive film A and the observation auxiliary member 2 and the light transmissive film A It is preferable to provide a filling means for interposing the filler 4 between the auxiliary member for observation 2.

  Examples of the filling means include a liquid filling means 7 that fills a liquid as the filler 4 between the other surface A2 of the light transmissive film A and the auxiliary member for observation 2. The liquid filling means 7 in this embodiment closely contacts the light transmissive film A and the observation auxiliary member 2 by interposing a liquid between the other surface A2 of the light transmissive film A and the auxiliary observation member 2. It is provided to make it. As the liquid, an appropriate liquid 4 that is easily filled between the light transmissive film A and the observation auxiliary member 2 and does not affect the final quality of the light transmissive film A is used. Examples of such liquids include volatile solvents such as water (pure water) and methyl ethyl ketone, and oil-based liquids such as essential oils.

  The liquid filling means 7 is constituted by an observation auxiliary member 2 constituted by a roll and a storage container 20. The liquid is stored in the storage container 20, and a part (lower part) of the observation auxiliary member 2 is immersed in the liquid in the storage container 20.

  In the liquid filling means 7 configured as described above, when the observation auxiliary member 2 is rotated, the liquid 4 is supplied to the surface of the observation auxiliary member 2, and the observation auxiliary member 2 is further rotated. The liquid 4 is filled between the light transmissive film A and the observation auxiliary member 2, and the light transmissive film A and the observation auxiliary member 2 are in close contact with each other through the liquid. For this reason, the penetration | invasion of the air between the transparent film A and the auxiliary member 2 for observation is suppressed, and it is suppressed that a clearance gap produces between both.

  FIG. 3 shows another example of the liquid filling means 7. This liquid filling means 7 is constituted by filling the filling tank 21 of the auxiliary member for observation 2 provided with a filling tank 21 opening upward on the surface with a liquid. The light transmissive film A is conveyed so as to cross the opening of the filling tank 21 of the observation auxiliary member 2. At this time, the imaging unit 1 images reflected light from the light transmissive film A disposed in the opening of the filling tank 21. In such a liquid filling means 7, when the light transmissive film A is imaged, the liquid 4 in the filling tank 21 is interposed between the light transmissive film A and the observation auxiliary member 2, and the light transmissive film A is transmitted. Of air between the conductive film A and the auxiliary member for observation 2 is suppressed.

  In this way, the filler 4 such as a liquid is filled between the light transmissive film A and the observation auxiliary member 2, and the other surface A2 on the observation auxiliary member 2 side of the light transmissive film A and the observation auxiliary member 2 are filled. If the air between the two is excluded, the reflected light from the other surface A2 of the observation auxiliary member 2 side of the light transmissive film A can be suppressed. That is, as shown in FIG. 5A, air is present in the gap S between the other surface A2 of the light transmissive film A and the outer surface of the observation auxiliary member 2 without the filler 4 such as a liquid interposed. The light L3 reflected on one surface A1 of the light transmissive film A and the light L4 reflected on the other surface A2 through the light transmissive film A are produced, and these lights L3 and L4 are mixed. Since the light enters the imaging unit 1 while interfering with each other, there is a possibility that the detection accuracy of the defect is lowered. On the other hand, as shown in FIG. 5 (b), when the air in the gap between the other surface A2 of the light transmissive film A and the outer surface of the observation auxiliary member 2 is excluded, a filler 4 such as a liquid is interposed. The light L4 that has passed through the light transmissive film A travels toward the liquid and is absorbed by the observation auxiliary member 2, so that almost no light is reflected from the other surface A2 of the light transmissive film A. Therefore, the light L3 reflected by the one surface A1 of the light transmissive film A enters the imaging unit 1 without interference, and the defect detection accuracy is increased.

  In particular, when the observation auxiliary member 2 is subjected to a surface roughening treatment, air is likely to be formed between the light-transmitting film A and the observation auxiliary member 2, but such a gap is likely to occur. If the liquid filling means is provided in this case, the reflected light from the observation auxiliary member 2 is reduced, and the reflected light from the other surface A2 of the light-transmitting film A is also reduced, and high defect detection accuracy is exhibited. The

  Of course, even when the observation auxiliary member 2 is subjected to a reflectance reduction process other than the roughening process, the defect detection device may be provided with a filling means. Even when the reflectance reduction process is not performed, the defect detection apparatus may be provided with a filling unit.

  Further, when the filling means as described above is provided, the air between the other surface of the light transmissive film A and the observation auxiliary member 2 is excluded by the filling means as a reflectance reduction process. Further, a colored filling process in which the colored filler 4 is interposed may be performed. Examples of the colored filler 4 include a liquid colored in a colored color such as black by blending a pigment or the like. In this case, the amount of light in the specific wavelength range that reaches the observation auxiliary member 2 is reduced by coloring the filler 4 in an appropriate color so as to absorb the light in the specific wavelength range, and as a result. The reflected light in the specific wavelength region from the observation auxiliary member 2 is reduced. In particular, when the filler 4 is colored black, the reflected light in a wide visible region is reduced, and when the specific wavelength region is included in the visible light region, the reflection is performed regardless of the value of the specific wavelength region. Light is reduced.

  In addition, as the reflectance reduction process, a colorization process for coloring the surface of the auxiliary observation member 2 may be used. As such a coloring process, the surface of the observation auxiliary member 2 is formed of a colored material such as black, or the surface of the observation auxiliary member 2 is painted to be black or the like. Can be mentioned. In this case, the reflected light in the specific wavelength region from the observation auxiliary member 2 is reduced by coloring the surface color of the observation auxiliary member 2 to an appropriate color so as to absorb the light in the specific wavelength region. To do. In particular, when the surface of the observation auxiliary member 2 is colored black, the reflected light in a wide visible region is reduced, and when the specific wavelength region is included in the visible light region, the value of the specific wavelength region is obtained. Regardless, the reflected light is reduced.

  In addition, by applying a paint containing a light-absorbing material that absorbs light in the specific wavelength region to the surface of the observation auxiliary member 2, reflected light in the specific wavelength region from the surface of the observation auxiliary member 2 is reflected. It can also be reduced.

  Only one type of the reflectance reduction processing as described above may be performed, or a plurality of types of reflectance reduction processing may be combined.

It is the schematic which shows an example of embodiment of this invention. It is a partial schematic diagram showing another example of the embodiment of the present invention. It is a partial schematic diagram showing still another example of the embodiment of the present invention. (A) And (b) is a schematic sectional drawing which shows an example of a structure of a light transmissive film, and the mode of the defect which arises in this light transmissive film. (A) (b) is the expanded schematic which shows the effect | action of a filler.

Explanation of symbols

DESCRIPTION OF SYMBOLS A Light transmissive film 1 Imaging part 2 Observation auxiliary member 3 Detection means 4 Filler 6 Illumination means 8 Base film 9 Coating layer

Claims (4)

A defect detection device for detecting defects in a light transmissive film provided with a coating layer on one side of a base film,
A conveying means for conveying the light transmissive film;
A plurality of illumination means for irradiating light from one side to the light transmissive film,
A plurality of imaging units that receive and image light received from the plurality of illumination means and reflected from one surface of the light transmissive film, and defects in the light transmissive film from images obtained by imaging by the imaging unit Comprising detecting means for detecting
Each illumination unit constituting the plurality of illumination units and each imaging unit constituting the plurality of imaging units are provided along a route to be conveyed,
Each imaging unit of the plurality of imaging units has different specific wavelength ranges for receiving light, and is provided corresponding to each illumination unit of the plurality of illumination units. .   The defect detection device for a light transmissive film according to claim 1, wherein the imaging unit includes a wavelength filter that allows light in a specific wavelength range to pass therethrough.   An auxiliary member for observation is provided on the other surface side of the light transmissive film to be imaged by the imaging unit and subjected to a reflectance reduction process for reducing the reflectance of light in a specific wavelength range. The defect detection apparatus of the light transmissive film of Claim 1 or 2. An auxiliary member for observation arranged on the other surface side of the light transmissive film imaged by the imaging unit;
A filling means for closely attaching the light transmissive film and the observation auxiliary member by interposing a filler between the other surface of the light transmissive film and the auxiliary member for observation;
The defect detection apparatus for a light transmissive film according to claim 1, wherein the filler absorbs light in a specific wavelength region.

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