JP5904982B2 - Casting apparatus, solution casting equipment and method - Google Patents

Description

  The present invention relates to a casting apparatus, a solution casting apparatus, and a method.

  Polymer films (hereinafter referred to as “films”) are widely used as optical functional films because of their features such as excellent light transmittance, flexibility, and reduction in weight and thickness. Among them, cellulose ester films using cellulose acylate are toughness and low birefringence, and are constituent members of liquid crystal display devices whose market has been expanding in recent years including photographic photosensitive films. It is used as a protective film for polarizing plates or an optical compensation film.

  Main film production methods include a solution casting method and a melt extrusion method. In the solution casting method, a polymer solution containing a polymer and a solvent (hereinafter referred to as a dope) is allowed to flow as a bead on a support. The bead becomes a cast film on the support. After the cast film has self-supporting properties, it is peeled off from the support to form a wet film. Furthermore, this wet film is dried to form a film. Compared with the melt extrusion method in which a melted polymer is extruded with an extruder to form a film, the solution casting method is superior in optical isotropy and thickness uniformity, and can obtain a film containing less foreign substances. Functional films are mainly manufactured by a solution casting method.

  The production rate of the solution casting method is considered to be rate-limiting in the casting process of forming a casting film from the dope. Therefore, in order to increase the productivity of solution casting, it is a problem to speed up the casting process. In order to perform the casting process at high speed, for example, the traveling speed of the support is increased. However, in the vicinity of the surface of the traveling support, wind that flows in the traveling direction together with the support (hereinafter referred to as accompanying wind) is generated as the support travels. When this accompanying wind hits the bead, the bead vibrates. This vibration of the bead causes a film thickness unevenness failure in the film width direction. Such a thickness unevenness failure caused by the accompanying wind becomes remarkable when the traveling speed of the support increases. Therefore, as disclosed in Patent Document 1, a wind shield is disposed near the bead on the upstream side in the support running direction with respect to the bead to prevent the accompanying wind from entering the bead.

  Further, as disclosed in Patent Document 2, a decompression chamber is arranged in the vicinity of the bead on the upstream side in the running direction of the support with respect to the bead, the accompanying wind is sucked by negative pressure, and the vibration of the bead due to the accompanying wind is reduced. It is suppressed.

JP 2004-114328 A JP 2010-158834 A

  By the way, with the recent increase in size and weight of flat panel displays, the film to be formed is also becoming thinner. In order to efficiently produce a thin film, in addition to forming a thin film by stretching in the stretching process after film formation, it is preferable to reduce the thickness from the bead stage, and improvements have also been made for thinning the bead.

  However, when the bead is made thin at the casting stage, even if there is no problem with the conventional bead thickness, if the bead becomes thin, it becomes more susceptible to the accompanying wind. As a method of thinning this bead, there is no change in the bead thickness at the discharge port of the die as in the conventional case, and the thickness immediately before the bead contacts the support is reduced by increasing the moving speed of the support, In some cases, the bead thickness of the discharge outlet is made thinner than the conventional one.

  For example, when a windshield as in Patent Document 1 is arranged close to the support and the accompanying wind accompanying the movement of the support is blocked by the windshield, when the bead is made thin and cast, There is a long unevenness in the thickness, which changes in the feed direction of the support, and thus appears as a planar failure that changes into a waveform in the feed direction, and there is a demand for improvement.

  In addition, when a decompression chamber is used as in Patent Document 2, the bead is liable to vibrate due to the pneumatic vibration generated by the negative pressure as the bead is thinned, and a similar surface failure has appeared. There is a request. In addition, air entrainment easily occurs due to vibration of the bead. When air is caught between the support and the bead, the air enters between the casting film formed by casting the bead on the support and the support. This air entrainment may develop into tearing of the cast film. In this case, the casting is stopped, and it takes a lot of time and labor to start casting. Therefore, there is a demand to suppress air entrainment.

  The present invention enables high-speed casting to improve productivity when a thin film is formed into a solution, and can further suppress the occurrence of surface deterioration or casting stop due to air entrainment. An object is to provide an apparatus, a solution casting apparatus, and a method.

In order to achieve the above object, the present invention includes a die, a wind shielding member, and an accompanying wind guide surface. The die discharges the dope from the discharge port toward the traveling support and forms a bead with the support. The bead becomes a cast film on the surface of the support. The wind-shielding member is provided in the width direction of the cast film on the upstream side of the support in the running direction of the support. This wind-shielding member is disposed so as to be close to the surface of the support, and blocks the accompanying wind by the support to the beads. The accompanying wind guide surface is formed in a portion close to the surface of the support and guides the accompanying wind to the die. The gap between the accompanying wind guide surface and the support surface increases toward the bead, and guides the accompanying wind from a position close to the support surface toward the side surface of the die.

The accompanying wind guide surface is preferably a curved surface that swells downward. It is preferable that the curved surface has a porous layer having a smooth surface, and the accompanying air is sucked from the porous layer. Further, it is preferable that the curved surface has a groove extending in the width direction of the casting film, and the accompanying air is sucked from the groove.

The exit end of the accompanying air guide surface has a distance of 2 mm or more from the discharge port along the side surface of the die to the upstream side in the running direction of the support, and the accompanying air sent along the accompanying air guide surface is sucked by the suction passage. It is preferred that Moreover, it is preferable that the distance of a wind-shielding member and the support surface is 0.1 mm or more and 3 mm or less, and the length in the running direction of an accompanying wind guide surface is 10 mm or more and 40 mm or less.

  The solution casting apparatus of the present invention includes the above casting apparatus and a drying apparatus that peels off the casting film from the support and dries it. Moreover, the solution casting method of this invention has the process of forming a cast film on a support body using said casting apparatus, and the process of peeling and peeling a cast film from a support body.

  According to the present invention, it is possible to efficiently manufacture a thin film while suppressing the occurrence of thickness unevenness failure.

It is a side view which shows the outline | summary of the solution casting apparatus of this invention. It is a perspective view which shows the outline | summary of a casting apparatus. It is sectional drawing which shows the flow of the accompanying wind between die | dye, a windshield block, and a band in 1st Embodiment. It is sectional drawing which shows the porous layer and suction channel | path of a windshield block of 2nd Embodiment. It is sectional drawing which shows the flow of the entrainment wind in a porous layer. It is a reverse view of the windshield block which shows a porous layer. It is sectional drawing which shows the suction groove of the wind-shielding block of 3rd Embodiment. It is a reverse view which shows the suction groove of a windshield block. It is sectional drawing which shows the wind-shielding block of 4th Embodiment which has an entrance guide part. It is sectional drawing which shows the flow of the accompanying wind in the conventional windshield block.

  As shown in FIG. 1, the solution casting apparatus 10 includes a casting apparatus 11, a first tenter 12, a drying apparatus 13, a second tenter 14, a slitter 15, and a winding apparatus 16. Are connected in series in order from the upstream side.

  The casting apparatus 11 includes drums 21 and 22, endless bands (supports) 23 spanning the drums 21 and 22, a guide roller 24, a die 25, ducts (membrane dryers) 26 </ b> A, 26 </ b> B, 26C and a stripping roller 28. The band 23 functions as a metal casting support body formed in an annular shape, and is stretched around the peripheral surfaces of the first drum 21 and the second drum 22. The first drum 21 is rotationally driven by a motor (not shown), whereby the band 23 travels in the first direction indicated by the arrow A. The guide roller 24 supports the upper band 23 from the back side.

  As shown in FIG. 2, a die 25 is disposed above the first drum 21. The die 25 continuously flows from the discharge port 25 </ b> A (see FIG. 3) with the dope 30 as a bead 31 on the surface of the traveling band 23. Thereby, the casting film 32 is formed on the band 23. The dope 30 is obtained by, for example, dissolving cellulose acylate in a solvent, and is produced by a dope production line (not shown) and supplied to the die 25.

  As shown in FIG. 1, the casting film 32 toward the peeling roller 28 is heated by the second drum 22 and the band 23 in order to improve the manufacturing speed. Further, at the casting position, the band 23 is cooled by the first drum 21 so that the temperature of the band 23 does not rise excessively. For this reason, each drum 21 and 22 has a temperature control device (not shown).

  A plurality of ducts 26 </ b> A, 26 </ b> B, and 26 </ b> C are arranged along the traveling path of the band 23, and blow dry air. The hot air controller controls the temperature, humidity, and flow rate of the drying air independently. The temperature of the casting film 32 is adjusted by controlling the temperature and flow rate of the drying air and the temperature control by the temperature control device of the drums 21 and 22 itself, and the solvent is evaporated from the casting film 32, Drying proceeds. Then, the casting film 32 is solidified to such an extent that it can be conveyed by the first tenter 12.

  A peeling roller 28 is disposed near the peripheral surface of the first drum 21 on the upstream side in the running direction with respect to the die 25. The peeling roller 28 supports the casting film 32 when the casting film 32 that has been dried in a state containing a solvent is peeled off from the band 23. The cast film 32 thus peeled off is guided to the first tenter 12 as a film 33.

  In the first tenter 12, the side edges of the film 33 are gripped by the clips 34, and a dry air is sent from the duct 36 to apply tension in the film width direction while conveying the film 33. Increase the width.

  In the drying device 13, the film 33 is wound around a number of rollers 38 and conveyed. The atmosphere inside the drying device 13 is controlled by a temperature controller (not shown) such as temperature and humidity, and the solvent evaporates from the film 33 while the film 33 is being transported.

  The second tenter 14 has the same structure as the first tenter 12 and includes a clip 35 and a duct 37. The second tenter 14 stretches while holding the film 33 with the clip 35. By this stretching, the film 33 having desired optical characteristics is obtained. Note that the second tenter 14 may not be used depending on the optical characteristics of the film 33.

  The slitter 15 cuts out the side portion including the retention marks by the clips 34 and 35 of the first tenter 12 and the second tenter 14. The film 33 whose side portion has been cut off is wound into a roll by the winding device 16. The roll film 33a obtained by the present invention can be used particularly for a retardation film and a polarizing plate protective film.

  A wind shield block (wind shield member) 41 is disposed upstream of the bead 31 from the die 25 in the traveling direction of the band 23. As shown in FIG. 2, the wind shielding block 41 is disposed in the width direction of the casting film 32 in the vicinity of the bead 31. The wind shield block 41 is attached to the die 25 via a spacer 45. The wind shield block 41 has the same length as the die 25 in the width direction of the band 23 indicated by the arrow B, and has an accompanying wind guide surface 42 facing the band 23. The accompanying wind guide surface 42 is disposed so as to be close to the surface of the band 23.

  The spacer 45 is spaced apart in the B direction, and forms a suction passage 46 between the side surface 25B of the die 25 and the upper slope 41A of the wind shield block 41. Since the band 23 travels at a high speed, the accompanying air 43 is generated along with the air. The wind blocking block 41 blocks the accompanying wind 43 on the upstream side of the bead 31 so that the accompanying wind 43 does not hit the bead 31.

  A gap G is provided between the two so that the wind shield block 41 does not contact the traveling band 23. For this reason, in the gap G between the band 23 and the wind shield block 41, the lower layer portion 43 </ b> A of the accompanying wind 43 that is not completely shielded passes through the gap G.

  As shown in FIG. 10, in the conventional case where the traveling speed of the band 101 is about 30 m / min, the accompanying wind 104 passing through the gap 103 between the wind shielding block 102 and the surface of the band 101 is directed to the bead 105. Therefore, it does not develop into a planar failure such as uneven thickness of the cast film 106. If the traveling speed of the band 101 is increased to 50 m / min or more and 100 m / min or less in accordance with the demand for thinning, the bead 105 becomes thinner and easily affected by the accompanying wind 104 as the speed increases. Conventionally, although the accompanying wind 104 is shielded by the wind shielding block 102, the lower layer portion 104 </ b> A of the accompanying wind 104 passing through the gap 103 winds the vortex 107 after passing through the shielding block 102. Generation | occurrence | production of this vortex 107, the vibration provision to the bead 105 by this vortex 107, etc. are confirmed by experiment of this inventor.

  For this reason, as shown in FIG. 3, in the first embodiment, the gap G with the surface of the band 23 is gradually set so that the accompanying wind guide surface 42 of the wind-shielding block 41 gradually moves away from the band 23 toward the bead 31. It is getting bigger. Further, the accompanying wind guide surface 42 is formed as a curved surface convex downward so that the accompanying wind 43 flows smoothly along the guide surface 42. Further, the outlet end 42 </ b> B of the accompanying wind guide surface 42 is positioned on the side surface 25 </ b> B of the die 25. Therefore, by moving the lower layer portion 43A of the accompanying air 43 along the accompanying air guide surface 42 and guiding it toward the side surface 25B of the die 25, the accompanying air 43 toward the bead 31 can be reduced by that amount. The bead 31 is stabilized and the occurrence of air entrainment is eliminated. The accompanying wind guide surface 42 is a curved surface convex downward, but it may be a flat surface. In FIG. 3, hatching between the die 25 and the wind shielding block 41 is omitted in order to avoid complication of the drawing.

  At the inlet end 42 </ b> A of the wind shield block 41, the upper layer portion 43 </ b> B of the accompanying wind 43 is blocked by the wind shield block 41. In addition, a part of the accompanying wind lower layer portion 43 </ b> A that flows along the accompanying wind guide surface 42 hits the side surface 25 </ b> B of the die 25 without hitting the bead 31. The accompanying air 43 hitting the side surface 25B of the die 25 is sent to the upper portion of the die 25 by the suction passage 46. Further, the accompanying air 43 that flows along with the band 23 without being along the accompanying air guide surface 42 is reduced by the amount of the accompanying air 43 that has flowed on the accompanying air guide surface 42, and vibration of the beads 31 and air entrainment are suppressed.

  The accompanying wind guide surface 42 has an entrance-side gap G1 with the band 23 of 0.1 mm to 3 mm, preferably 0.5 mm to 2 mm. If it is less than 0.1 mm, it is not preferable because it comes into contact with the band 23 due to a temperature change or foreign matter on the band 23. Moreover, if it exceeds 3 mm, an accompanying wind cannot be interrupted | blocked and the effect of a windshield will not be acquired. Moreover, the exit side gap G2 is 3 mm or more and 20 mm or less, preferably 5 mm or more and 10 mm or less. If it is less than 3 mm, even if the accompanying wind is induced, the accompanying wind cannot be separated from the bead, and the surface condition improving effect cannot be obtained. Moreover, if it exceeds 20 mm, the induced accompanying wind will be disturbed on the way, and the surface improvement effect cannot be obtained.

The length L1 in the A direction of the accompanying wind guide surface 42 is 10 mm or more and 40 mm or less, preferably 20 mm or more and 30 mm or less. If it is less than 10 mm, the accompanying wind cannot be separated from the bead even if the accompanying wind is induced, and the surface improvement effect cannot be obtained. Moreover, if it exceeds 40 mm, the induced accompanying wind will be disturbed on the way or it will become impossible to guide, and the surface improvement effect cannot be obtained. Further, the outlet end 42B of the accompanying wind guide surface 42 has a distance L2 from the discharge port 25A of the die 25 of 2 mm or more, preferably 3 mm or more. If it is less than 2 mm, the induced accompanying wind hits the bead, and the surface improvement effect cannot be obtained.

  As shown in FIGS. 4-6, in 2nd Embodiment, the porous layer 51 and the suction passage 52 are provided in the accompanying wind guide surface 42 with respect to the wind shielding block 41 of 1st Embodiment, and wind shielding is carried out. Block 53 is formed. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. As shown in FIG. 6, the porous layer 51 is formed long in the B direction. The surface of the porous layer 51 is formed smoothly. The term “smooth” as used herein means that the arithmetic surface roughness Ra is 30 μm or less. By setting Ra to 30 μm or less, it is possible to guide the die toward the die without disturbing the accompanying wind.

  The suction passage 52 is formed on the back surface (inner surface) of the porous layer 51. The suction passage 52 is connected to a negative pressure source 54 provided outside the wind shield block 53. Therefore, the accompanying air 43 is sucked when passing through the porous layer 51. Thereby, since most of the accompanying wind 43 is guided to the accompanying wind guide surface 55 side, the accompanying wind 43 that hits the bead 31 can be reduced accordingly.

  As shown in FIGS. 7 and 8, in the third embodiment, instead of the porous layer 51, the suction groove 61 is formed along the B direction on the accompanying wind guide surface 60 to configure the wind shielding block 62. Is. The suction groove 61 has a circular cross section and has a suction port 61A at the lower end. A plurality of, for example, three suction grooves 61 are arranged in the A direction. Both ends of the suction groove 61 are connected to the negative pressure source 54. Therefore, the accompanying air 43 passing through the gap G is sucked by the suction groove 61 and is discharged from both sides of the wind shielding block 62.

  As shown in FIG. 9, in 4th Embodiment, the entrance guide part 71 was provided in the entrance side of the wind-shielding block 41 of 1st Embodiment, and the wind-shielding block 72 was comprised, The basic composition is This is the same as the wind shield block 41 of the first embodiment. The inlet guide portion 71 has an acute angle in order to efficiently separate the accompanying air 43 into the lower layer portion 43A and the upper layer portion 43B. The inlet guide portion 71 has an upper layer accompanying wind guide surface 74 that is in contact with the lower layer accompanying wind guide surface 73 at an acute angle obliquely from above. Therefore, the wind shield block 72 has a substantially triangular shape in the longitudinal section due to the lower layer accompanying wind guide surface 73, the upper layer accompanying wind guide surface 74, and the suction passage surface 75. In addition, the porous layer 51 as in the second embodiment or the suction groove 61 as in the third embodiment may be formed in the lower layer accompanying wind guide surface 73.

  In each of the above embodiments, the suction pressure BP by the suction passage 46, the suction passage 52, and the suction groove 61 is −0.5 Pa to −100 Pa, preferably −1 Pa to −50 Pa. If it is less than −0.5 Pa, the accompanying wind cannot be sufficiently induced. On the other hand, if it exceeds −100 Pa, the bead itself is also deformed by the negative pressure, and the surface condition is deteriorated.

  In each of the above embodiments, the wind shielding blocks 41, 53, 62, 72 are provided on the upstream side in the running direction with respect to the die 25. Further, a decompression chamber is provided upstream of the wind shielding blocks 41, 53, 62, 72. It may be provided. The decompression chamber sucks the air in the upstream area of the bead 31 to decompress the inside of the area, and reduces the vibration of the bead 31.

  In the second embodiment, the porous layer 51 is formed on the inlet end side of the accompanying air guide surface 42, but the porous layer 51 may be formed over the entire surface of the accompanying air guide surface 42.

  In the solution casting apparatus 10 of the present invention, the width of the film 33 as a product is preferably 600 mm or more, and more preferably 1400 mm or more and 2500 mm or less. It is also effective when the width of the film 33 is larger than 2500 mm. The film 33 has a thickness of preferably 15 μm or more and 80 μm or less, particularly preferably 15 μm or more and 60 μm or less, and further preferably 15 μm or more and 40 μm or less. The polymer used as the raw material of the film 33 is not particularly limited, and examples thereof include cellulose acylate and cyclic polyolefin.

Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. The ratio in which the hydroxyl group of cellulose is esterified with carboxylic acid, that is, the substitution degree of the acyl group satisfies all of the following formulas (I) to (III) is preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group, A is the substitution degree of the acetyl group, and B is the substitution degree of the acyl group having 3 to 22 carbon atoms. It is. Moreover, it is preferable that 90 weight% or more of triacetylcellulose (TAC) is a particle | grain of 0.1 mm-4 mm.
(I) 2.0 ≦ A + B ≦ 3.0
(II) 1.0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9

  The total substitution degree A + B of the acyl group is more preferably 2.20 or more and 2.90 or less, and particularly preferably 2.40 or more and 2.88 or less. Further, the substitution degree B of the acyl group having 3 to 22 carbon atoms is more preferably 0.30 or more, and particularly preferably 0.5 or more.

  Details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148. These descriptions are also applicable to the present invention. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, and release accelerators. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516].

  Experiments were conducted to confirm the effects of the wind shielding blocks 41, 53, 62, and 72 of the present invention. In Example 1, as shown in FIG. 3, the bead 31 is stabilized by using the wind shielding block 41 having the accompanying wind guide surface 42, and the solution casting apparatus 10 shown in FIG. After the casting film 32 is formed, the casting film 32 is peeled off to form a film 33. The film 33 is manufactured through the first tenter 12, the drying device 13, and the second tenter 14, and the film 33 is formed into a roll shape. Winded up. In Example 2, as shown in FIGS. 4 to 6, a film 33 was manufactured under the same conditions as in Example 1 except that a wind shield block 53 having a porous layer 51 on the accompanying wind guide surface 42 was used. In Example 3, as shown in FIGS. 7 and 8, the film 33 was manufactured under the same conditions as in Example 1 except that a wind shield block 62 having a suction groove 61 on the accompanying wind guide surface 60 was used. In Example 4, as shown in FIG. 9, the film 33 was manufactured under the same conditions as in Example 1 except that a wind shielding block 72 having an inlet guide portion 71 was used.

  In Comparative Example 1, a film 33 was produced under the same conditions as in Example 1 except that the conventional wind shield block 102 shown in FIG. 10 was used. In Comparative Example 2, a film 33 was produced under the same conditions as in Example 1 except that the windshield block was removed from Example 1.

  In Examples 1 to 4, the thickness unevenness was 0.2 μm, and the castable limit speed was 80 m / min. On the other hand, in Comparative Example 1, the thickness unevenness was 0.4 μm, and the possible casting speed limit was 40 m / min. Further, in Comparative Example 2, the thickness unevenness was 0.8 μm, and the castable limit speed was 40 m / min. From the above results, it can be seen that the thickness unevenness has been improved and the castable limit speed has increased.

  The thickness unevenness is the difference between the maximum value and the minimum value of the thickness variation in the casting direction of the film in the dry film state, and the thickness variation is measured using a contact or non-contact type film thickness meter. Thickness unevenness was determined. The casting limit is determined by the presence or absence of air entrainment. The occurrence of air entrainment was confirmed by visually confirming the vicinity of the landing point of the bead and whether or not bubbles entered between the bead and the band at the landing point.

DESCRIPTION OF SYMBOLS 10 Solution casting apparatus 11 Casting apparatus 23 Band 25 Die 30 Dope 31 Bead 32 Casting film 33 Film 41, 53, 72 Wind-shielding block 42, 55, 60, 73: Entrainment wind guide surface 43 Accompaniment wind G Clearance 51 Porous Layer 52 Suction passage 61 Suction groove

Claims (8)

A die that forms a casting film on the surface of the support, while discharging a dope from a discharge port toward the traveling support, and forming a bead with the support,
Wind shielding that is provided in the width direction of the casting film on the upstream side in the running direction of the support relative to the bead and is arranged so as to be close to the surface to block the accompanying wind by the support to the bead Members,
Formed in a portion near the surface of the wind-shielding member, a gap with the surface is gradually increased toward the bead, and the accompanying air is guided from the position close to the surface toward the side surface of the die. A wind guide surface,
A casting apparatus having The casting apparatus according to claim 1, wherein the accompanying wind guide surface is a curved surface that swells downward .   The casting apparatus according to claim 2, wherein the curved surface has a porous layer having a smooth surface, and sucks the accompanying air from the porous layer.   The casting apparatus according to claim 2, wherein the curved surface has a groove extending in a width direction of the casting film, and sucks accompanying air from the groove. The exit end of the accompanying air guide surface has a distance of 2 mm or more from the discharge port along the side surface of the die to the upstream side in the running direction of the support, and the accompanying air is sent along the accompanying air guide surface. The casting apparatus according to any one of claims 1 to 4, wherein the is sucked by a suction passage. The distance between the air shielding member and the surface is at 0.1mm or 3mm or less, the entrained air length in the traveling direction of the guide surface from claim 1 is 10mm or more 40mm or less 5 according to any one of Casting equipment. A casting apparatus according to any one of claims 1 to 6;
Solution casting apparatus and a drying device for drying by peeling the casting film from the support. Forming the casting film on the support using the casting apparatus according to any one of claims 1 to 6;
And a step of peeling the cast film from the support and drying it.

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