JP2015060148A - Method for manufacturing retardation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce optical defects caused by deformation near the surface of an acrylic substrate original sheet in a roll state in manufacturing a retardation film.SOLUTION: A method for manufacturing a retardation film is provided, in which the retardation film comprises an acrylic resin film substrate and an alignment film and a retardation layer laminated on the film substrate; the method includes an alignment film formation step which further includes a step of supplying the film substrate from a roll body of long sheet having a predetermined width and applying a resin composition to constitute the alignment film on one surface of the film substrate. The film substrate constituting the roll body has a coefficient of variation of 1.3% or more in thickness distribution in a width direction; and the roll body is wrapped in a moisture-proof state by a moisture-proof film having water vapor permeability of 0.1 g/(mday atm) or less at 40°C and 90% humidity until just before the alignment film formation step.

Description

  The present invention relates to a method for producing a retardation film such as a pattern retardation film applied to, for example, a passive three-dimensional image display.

  Conventionally, flat panel displays have been mainly two-dimensional displays. However, in recent years, flat panel displays capable of three-dimensional display have attracted attention, and some are also commercially available. Further, there is a tendency that future flat panel displays are capable of three-dimensional display, and flat panel displays capable of three-dimensional display are being studied in a wide range of fields.

  In order to perform three-dimensional display on a flat panel display, it is usually necessary to selectively provide a right-eye image and a left-eye image in some manner, respectively, to the viewer's right eye and left eye. As a method for selectively providing a right-eye video and a left-eye video, for example, a passive method is known. This passive three-dimensional display method will be described with reference to the drawings. FIG. 7 is a schematic diagram showing an example of a passive three-dimensional display using a liquid crystal display panel. In the example of FIG. 7, pixels that are consecutive in the vertical direction of the liquid crystal display panel are sequentially and alternately assigned to a right-eye pixel that displays a right-eye image and a left-eye pixel that displays a left-eye image. And the image data for the left eye, and thereby the image for the right eye and the image for the left eye are simultaneously displayed. In this way, the screen of the liquid crystal display panel is alternately divided into a region for displaying a right-eye image and a region for displaying a left-eye image by a strip-shaped region having a short side in a vertical direction and a long side in a horizontal direction. Will be.

  Furthermore, in the passive method, a pattern retardation film is placed on the panel surface of the liquid crystal display panel, and light emitted from the linearly polarized light from the right-eye and left-eye pixels is converted into circularly polarized light with different rotation directions for the right-eye and left-eye. To do. For this reason, in the pattern retardation film, two types of band-like regions in which the slow axis direction (direction in which the refractive index is maximum) are orthogonal to each other are sequentially formed corresponding to the setting of the region in the liquid crystal display panel. Accordingly, in the passive method, glasses (glasses) each having a corresponding polarizing filter are attached, and a right eye image and a left eye image are selectively provided to the viewer's right eye and left eye, respectively. Incidentally, the slow axis direction of the adjacent strip-like region is usually any combination of +45 degrees and −45 degrees, 0 degrees and +90 degrees, and 0 degrees and −90 degrees with respect to the horizontal direction. In the example of FIG. 7, the long side direction of the screen is shown as the horizontal direction in accordance with the name in the normal image display apparatus. In the passive method, the pixels that are continuous in the horizontal direction in FIG. 7 are driven by being distributed to the belt-like region having the long side in the vertical direction (the short side direction of the screen) for the right eye and the left eye, and to cope with this. Even when a pattern retardation film is prepared, a three-dimensional image can be displayed in the same manner.

  This passive method can also be applied to a liquid crystal display device with a slow response speed, and can also display three-dimensionally with a simple configuration using a pattern retardation film and circularly polarized glasses. Therefore, the passive liquid crystal display device has been attracting a great deal of attention as a center of the future three-dimensional display device.

  The pattern phase difference film according to this passive method requires a pattern-like phase difference layer that gives a phase difference to transmitted light corresponding to the allocation of pixels. This pattern retardation film has not been widely researched and developed yet, and there is no established standard technology.

  With respect to this pattern retardation film, Patent Document 1 discloses a method for forming a retardation layer by forming a photo-alignment film with controlled alignment regulating force on a glass substrate and patterning the alignment of liquid crystals with this photo-alignment film. Is disclosed. Further, Patent Document 2 discloses a method for forming a photo-alignment film in which a fine uneven shape is formed around a roll plate by laser irradiation, and this uneven shape is transferred to control the alignment regulating force in a pattern shape. ing.

  Although it is desired that such a pattern retardation film can be mass-produced efficiently with high accuracy, the conventional method has a problem that is still insufficient in practice in terms of accuracy.

  Patent Document 3 discloses that the dimensional accuracy of the pattern retardation film is improved by adjusting the transparent film moisture content of a hygroscopic substrate such as TAC (triacetyl cellulose) to prevent expansion and contraction of the substrate. Is disclosed.

JP 2005-049865 A JP 2010-152296 A JP2013-140306A

  For example, when a retardation film is produced by sequentially laminating an alignment film and a retardation layer on a film substrate, the film base material (an antireflection layer, a hard coat layer, an electromagnetic shielding layer, etc. Is meant to include those laminated on the back side of the base material), and is usually a long roll-shaped winding body. By pulling out the film base material from here, it is sent to the next alignment film forming step .

  At this time, in the case of a wide and long winding body having a width of 1000 mm or more and a width of 1000 mm or more, for example, the original fabric is an acrylic resin, mainly due to the effect of moisture absorption on the winding body. During storage, deformation of the turtle shell pattern-like wrinkles or the like (hereinafter also simply referred to as original sheet deformation) may occur near the surface of the winding body (meaning the outside of the winding), particularly near the center in the width direction.

  Such a deformation of the raw material affects the thickness uniformity of the alignment film and the retardation layer, and appears as an optical defect such as a retardation defect after the production of the patterned retardation film. Need to be eliminated.

  The present invention has been made in view of such a situation, and an object of the present invention is to reduce optical defects due to deformation of an original fabric with respect to a retardation film such as a patterned retardation film according to a passive method.

  As a result of intensive research to solve the above problems, the present inventor has found that, in the case of an acrylic raw material, the deformation of the raw material is not only moisture absorption into the film base material, but also the thickness in the raw material width direction. It has been found that it occurs due to the influence of both the variation of the surface and the moisture absorption on the surface of the original fabric, and the present invention has been completed.

  Specifically, the present invention provides the following.

(1) A method for producing a retardation film in which an alignment film and a retardation layer are laminated on a film substrate of an acrylic resin,
In the alignment film forming step including the step of supplying the film substrate from a long winding body having a predetermined width and applying the resin composition constituting the alignment film on one surface of the film substrate.
The film base material constituting the wound body has a coefficient of variation of 1.3% or more in the thickness distribution in the width direction,
The winding body is moisture-proof packaged by a moisture-proof film having a water vapor permeability of 0.1 g / m ² · day · atm or less at 40 ° C. and 90% until immediately before the alignment film forming step. It is a manufacturing method of retardation film.

  (2) The retardation film manufacturing method according to (1), wherein the average thickness of the film base material is less than 50 μm.

According to (1), even if a certain amount of thickness unevenness is present in the film base of the acrylic resin (hereinafter also simply referred to as “acrylic original fabric”), it is 0.1 g / m ² · day · atm or less. By performing moisture-proof packaging with a moisture-proof film, it is possible to prevent the deformation of the raw material such as wrinkles generated near the surface of the raw material, and as a result, it is possible to produce a retardation film with less optical defects due to the deformation of the original material.

  According to the knowledge newly obtained by the present inventors, when the variation coefficient in the thickness distribution in the width direction of the acrylic film substrate is, for example, about 1.1%, that is, when the thickness unevenness of the acrylic raw material is small. Is difficult to cause deformation of the original fabric even if moisture is absorbed (see the comparative example described later). For this reason, it was not considered that the hygroscopic packaging was effective when an acrylic raw material having a low hygroscopic property as compared with TAC (triacetyl cellulose) was used.

  However, according to the present invention, even when there is a thickness unevenness of a predetermined value or more, the above optical defects can be reduced by using the moisture-proof packaging together. Can be greatly expanded.

  The above-described effect is remarkably obtained particularly when the average thickness of the film substrate is less than 50 μm. That is, as the average thickness is reduced, the deformation of the original fabric is likely to occur, and therefore the present invention is effective in the aspect (2) of the present invention.

  According to the present invention, when an acrylic raw material is used as a film substrate, it is possible to prevent deformation of the raw material such as wrinkles generated near the surface, and as a result, a retardation film with less optical defects due to the raw material deformation is produced. it can.

It is a figure which shows an example of the retardation film of this invention. It is a flowchart which shows the manufacturing process of the pattern phase difference film of FIG. It is a figure where it uses for description of the exposure process of FIG. It is a figure which shows the film thickness distribution in Example 1. FIG. It is a figure which shows the film thickness distribution in the comparative example 3. It is a figure which shows the film thickness distribution in the comparative example 4. It is a figure where it uses for description of the three-dimensional image display by a passive system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing a patterned retardation film according to an embodiment of the present invention. In the image display device according to this embodiment, the pixels of the liquid crystal display panel that are continuous in the vertical direction (the left-right direction in FIG. 1) sequentially display the right-eye pixel for displaying the right-eye image and the left-eye image. They are distributed to the left-eye pixels to be displayed, and are driven by right-eye and left-eye image data, respectively. As a result, the image display device alternately divides the display screen into a band-like region for displaying an image for the right eye and a band-like region for displaying an image for the left eye, so that the image for the right eye and the image for the left eye are divided. Display at the same time. In this image display device, the pattern phase difference film 1 shown in FIG. 1 is disposed on the panel surface of the liquid crystal display panel, and the pattern phase difference film 1 corresponds to light emitted from pixels for the right eye and the left eye, respectively. To give the phase difference. Thereby, this image display apparatus displays a desired three-dimensional image by a passive method.

  In the pattern retardation film 1, an alignment film 3 and a retardation layer 4 are sequentially formed on a substrate 2 made of an acrylic transparent film material. In the pattern retardation film 1, the retardation layer 4 is formed of a liquid crystal material, and the alignment of the liquid crystal material is patterned by the alignment regulating force of the alignment film 3. The orientation of the liquid crystal molecules is indicated by a long and narrow ellipse in FIG. By this patterning, the pattern phase difference film 1 is formed in a band shape alternately with the right-eye area A and the left-eye area B sequentially with a certain width corresponding to the pixel assignment in the liquid crystal display panel. A phase difference corresponding to each of the light emitted from the right-eye and left-eye pixels is given. As the transparent film material, a material obtained by performing an antireflection film production process on the surface opposite to the surface on which the alignment film 3 and the retardation layer 4 are produced can be used.

  In the pattern retardation film 1, after a photo-alignment material film made of a photo-alignment material is produced, the alignment film 3 is formed by irradiating the photo-alignment material film with ultraviolet rays by linearly polarized light by a so-called photo-alignment technique. Here, the ultraviolet rays applied to the photo-alignment material film are set so that the direction of polarization is different by 90 degrees between the right-eye region A and the left-eye region B, whereby the liquid crystal material provided in the retardation layer 4 , Liquid crystal molecules are aligned in the corresponding directions in the right-eye region A and the left-eye region B, and a phase difference corresponding to transmitted light is given.

  FIG. 2 is a flowchart showing manufacturing steps of the pattern retardation film 1. In the manufacturing process of the pattern retardation film 1, the base material 2 is provided by a long transparent film material wound around a roll, and the base material 2 is fed out from a roller so that a photo-alignment material film is formed on the base material 2. (Step SP2). This SP2 is the alignment film forming step in the present invention. Here, although various manufacturing methods can be applied to the photo-alignment material film, in this embodiment, a film-forming liquid in which the photo-alignment material is dissolved in a solvent such as benzene is applied by a die and then dried. Is produced. Although various materials to which the photo-alignment technique can be applied can be applied as the photo-alignment material, in this embodiment, for example, a photo-dimerization type material is used. Examples of such a photodimerization type material include polymers having cinnamate, coumarin, benzylidenephthalimidine, benzylideneacetophenone, diphenylacetylene, stilbazole, uracil, quinolinone, maleinimide, or cinnamilidene acetic acid derivatives. Among them, a polymer having one or both of cinnamate and coumarin is preferably used in that the orientation regulating force is good. Specific examples of such a photodimerization type material include, for example, JP-A-9-118717, JP-T-10-506420, JP-T2003-505561, and WO2010 / 150748, “M. Schadt, K. Schmitt, V. Kozinkov and V. Chigrinov: Jpn. J. Appl. Phys., 31, 2155 (1992), “M. Schadt, H. Sieberle and A. Schuster: Nature, 381, 212 (1996). Can be mentioned.

  Subsequently, in this manufacturing process, a photo-alignment film is produced by irradiating ultraviolet rays in the exposure process (step SP3). Subsequently, in this manufacturing process, after the liquid crystal material is applied by a die or the like in the retardation layer manufacturing process, the liquid crystal material is cured by irradiation with ultraviolet rays, and the retardation layer 4 is manufactured (step SP4). Subsequently, in this manufacturing process, after performing an antireflection film manufacturing process or the like as necessary, in the cutting process, the pattern phase difference film 1 is manufactured by cutting out to a desired size (steps SP5 to SP6).

  FIG. 3 shows the details of this exposure process. This manufacturing process is performed by irradiating ultraviolet rays by linearly polarized light (polarized ultraviolet rays) through a mask 16A that shields the portion corresponding to the region A for the right eye or the region B for the left eye, For the left-eye region B or the right-eye region A, the photo-alignment material film is oriented in a desired direction (FIG. 3A). Thereby, this manufacturing process executes the first exposure process. Subsequently, this manufacturing process is opposite to the first exposure process, and the polarization direction of the first exposure process is 90 through the mask 16B that shields the part corresponding to the left eye region B or the right eye region A. The right-eye region A or the left-eye region B is subjected to an exposure process using different linearly polarized light, and the photo-alignment material film is oriented in a desired direction with respect to the right-eye region A or the left-eye region B (FIG. 3B). ). Thus, in this manufacturing process, the alignment film 3 is produced by sequentially exposing the region A for the right eye and the region B for the left eye by two exposure processes each using a mask.

[Film substrate]
The base material 2 corresponding to the film base material of the present invention is a transparent film material and has a function of supporting the alignment layer 3. In the present invention, it is a wide and long winding body. Here, the film base material in the present invention includes a material in which an antireflection layer, a hard coat layer, an electromagnetic wave shielding layer, or the like is laminated as necessary on the surface side of the base material on which the alignment film is formed. It is.

  The substrate 2 preferably has a small phase difference, and the in-plane retardation (in-plane retardation value, hereinafter also referred to as “Re value”) is preferably in the range of 0 nm or more and 10 nm or less, and 0 nm or more. More preferably, it is in the range of 5 nm or less, and further preferably in the range of 0 nm or more and 3 nm or less. If the Re value exceeds 10 nm, the display quality of the flat panel display using the alignment film may be deteriorated, which is not preferable.

Here, the Re value is an index indicating the degree of birefringence in the in-plane direction of the refractive index anisotropic body, and the refractive index in the slow axis direction having the largest refractive index in the in-plane direction is Nx, When the refractive index in the fast axis direction orthogonal to the axial direction is Ny, and the thickness in the direction perpendicular to the in-plane direction of the refractive index anisotropic body is d,
Re [nm] = (Nx−Ny) × d [nm]
It is a value represented by. The Re value can be measured by, for example, a parallel Nicol rotation method using a phase difference measuring device KOBRA-WR (manufactured by Oji Scientific Instruments). Further, in this specification, unless otherwise specified, the Re value means a value at a wavelength of 589 nm.

  The transmittance of the base material 2 in the visible light region is preferably 80% or more, and more preferably 90% or more. Here, the transmittance | permeability of a transparent film base material can be measured by JISK7361-1 (the test method of the total light transmittance of a plastic-transparent material).

  The base material 2 is a flexible base material having flexibility that can be wound up in a roll shape, and is an acrylic resin in the present invention. Specifically, from the acrylic polymer (acrylic resin) such as PMMA. A conventionally known acrylic base material can be used. An acrylic base material made of an acrylic resin such as PMMA has a refractive index of about 1.40 to 1.60, has no refractive index difference in the thickness direction of the base material, and has a low dimensional shrinkage dependency on humidity. Therefore, for example, the film thickness can be reduced as compared with TAC (triacetyl cellulose), which can contribute to the expansion of the viewing angle of the 3D panel.

  As thickness of the base material 2 comprised by an acrylic base material etc., it is preferable to exist in the range of 25 micrometers or more and 100 micrometers or less, and it is more preferable to exist in the range of 30 micrometers or more and 50 micrometers or less. If the thickness of the substrate 2 is less than 25 μm, it may not be possible to impart the necessary self-supporting property to the retardation film, which is not preferable. When the thickness of the base material 2 exceeds 100 μm, when the retardation film is long, when the long retardation film is cut into a single-phase retardation film, processing waste increases. Or wear of the cutting blade may be accelerated.

  Here, the long and wide winding body of the substrate 2 has a variation coefficient (= 100 × standard deviation / average value, also referred to as unit%, CV value) in the thickness direction distribution in the width direction of 1.3% or more. is there. In this embodiment, the coefficient of variation is obtained by measuring the thickness at intervals of 0.5 mm along the short direction with a film thickness measuring device. If the coefficient of variation is less than 1.3%, the thickness unevenness is small and smooth, and therefore, deformation of the original fabric is difficult to occur without performing moistureproof packaging described later. If the coefficient of variation exceeds 5.0%, the material will be deformed even if moisture-proof packaging described later is performed. In addition, it is preferable that the thickness distribution of the base material 2 in the width direction is in the range of the average thickness ± 1 μm to the average thickness ± 3 μm.

[Moisture-proof packaging of acrylic fabric]
Next, in this invention, the acrylic raw material which is the winding body of said base material 2 is moisture-proof-packed, and the base material 2 is pulled out and supplied in the alignment film formation process of SP2 after that. Specifically, the wound body is moisture-proof packaged by a moisture-proof film having a water vapor permeability at 40 ° C. and 90% of 0.1 g / m ² · day or less until immediately before the alignment film forming step. The water vapor transmission rate is a value measured according to JIS 7129.

  The term “immediately before the alignment film forming step” means within 24 hours from the start of the alignment film forming step, preferably until before the acrylic raw material is installed and supplied in SP2.

  The moisture-proof film only needs to have the water vapor permeability described above, and examples thereof include a conventionally known barrier film in which a vapor deposition layer or a metal foil is laminated on a base film. For example, an OPP / AL foil is dry-laminated via an adhesive ( The laminated film etc. which were laminated | stacked by the DL) method can be illustrated, and it does not specifically limit. Further, the packaging method is not particularly limited, but a conventionally known twist packaging or the like may be used, and an effect can be obtained even if it is not a complete hermetic seal.

  In the above description, the case where the liquid crystal display panel is used as the pattern retardation film is described. However, the present invention is not limited to this, and the case where the organic EL panel and the plasma display panel are used is assumed. In addition, the present invention can be widely applied to a case where a polarizing filter is provided integrally. Moreover, it can utilize also as retardation films other than a pattern retardation film.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Example 1]
An acrylic raw material having a thickness distribution shown in FIG. 4 having an average thickness of 40 μm and a coefficient of variation in the thickness distribution in the width direction of 1.3% (maximum minimum: 40 μm ± 3 μm) is 1330 mm × 6000 m in width. Prepared as a winding body. The outside of the wound body was packed in a twist package with a moisture-proof film (water vapor permeability of 0.1 g / m ² · day or less) of OPP 20 μm / LDPE 15 μm / AL foil 7 μm / LDPE 15 μm. When the raw material deformation part was visually measured after storage for 1 month at an average of 23 ° C. and 50% RH, it was within 5 pieces. When the pattern retardation film shown in FIG. 1 was produced from this original fabric, the optical defects were within 5 pieces.

[Example 2]
An anti-glare layer (AG layer) is formed on the back side of the acrylic raw material of Example 1, the average thickness is 47 μm, and the variation coefficient in the thickness distribution in the width direction is 2.7% (maximum minimum is 47 μm ± 3 μm). As a result of carrying out in the same manner as in Example 1 except that the acrylic raw material with AG layer was used, the number of deformations of the raw material after one month was 10 or less, and the pattern retardation film shown in FIG. When manufactured, the optical defect was within 10 pieces.

[Example 3]
As a result of carrying out in the same manner as in Example 1 except that an acrylic raw material having an average thickness of 40 μm and a coefficient of variation in thickness distribution in the width direction of 1.5% (maximum minimum: 40 μm ± 3 μm) was used. The number of subsequent deformations of the original fabric was 5 or less. When the pattern retardation film shown in FIG. 1 was produced using this original fabric, the optical defects were 5 or less.

[Example 4]
An anti-glare layer (AG layer) is formed on the back surface of the acrylic raw material of Example 3, the average thickness is 47 μm, and the coefficient of variation in thickness distribution in the width direction is 3.5% (maximum minimum is 47 μm ± 3 μm). As a result of carrying out in the same manner as in Example 1 except that the acrylic raw material with AG layer was used, the number of deformations of the raw material after one month was 10 or less, and the pattern retardation film shown in FIG. When manufactured, the optical defect was within 10 pieces.

[Example 5]
As a result of carrying out in the same manner as in Example 1 except that an acrylic raw material having an average thickness of 40 μm and a coefficient of variation in thickness distribution in the width direction of 2.0% (maximum minimum: 40 μm ± 3 μm) was used. The number of subsequent deformations of the original fabric was 5 or less. When the pattern retardation film shown in FIG. 1 was produced using this original fabric, the optical defects were 5 or less.

[Example 6]
An anti-glare layer (AG layer) is formed on the back side of the acrylic raw material of Example 5, the average thickness is 47 μm, and the coefficient of variation in thickness distribution in the width direction is 4.0% (maximum minimum is 47 μm ± 3 μm). As a result of carrying out in the same manner as in Example 1 except that the acrylic raw material with AG layer was used, the number of deformations of the raw material after one month was 10 or less, and the pattern retardation film shown in FIG. When manufactured, the optical defect was within 10 pieces.

[Comparative Example 1]
As a result of carrying out in the same manner as in Example 1 except that aluminum vapor-deposited PET (water vapor transmission rate 0.5 g / m ² · day) was used as the moisture-proof film, the number of original fabric deformation portions after one month was about 50. When the patterned phase difference film shown in FIG. 1 was produced from the original fabric, there were about 50 optical defects.

[Comparative Example 2]
As a result of carrying out in the same manner as in Comparative Example 1 except that the acrylic raw material with an AG layer of Example 2 was used, the deformation of the original material became noticeable after 2 weeks, and the number of original material deformations after 1 month was several hundred. There were several hundred optical defects when the patterned retardation film shown in FIG.

[Comparative Example 3]
An acrylic raw material having an average thickness of 40 μm and a coefficient of variation in the thickness distribution in the width direction of 1.1% (maximum minimum: 38 μm ± 2 μm) having a thickness distribution shown in FIG. It was within several pieces when the raw-material deformation | transformation location was measured visually after 1 month storage on average 23 degreeC and 50% RH. When the pattern retardation film shown in FIG. 1 was produced from this original fabric, the optical defects were within several.

[Comparative Example 4]
A TAC (triacetyl cellulose) raw material having an average thickness of 60 μm and a coefficient of variation in the thickness distribution in the width direction of 0.9% (maximum minimum: 60 μm ± 3 μm) having the thickness distribution shown in FIG. It was within several pieces when the raw-material deformation | transformation location was measured visually after 1 month storage under 23 degreeC and 50% RH on average without a moisture-proof packaging. When the pattern retardation film shown in FIG. 1 was produced from this original fabric, the optical defects were within several.

DESCRIPTION OF SYMBOLS 1 Pattern retardation film 2 Base material 3 Orientation film 4 Phase difference layer 16A, 16B Mask

Claims (2)

A method for producing a retardation film in which an alignment film and a retardation layer are sequentially laminated on an acrylic resin film substrate,
In the alignment film forming step including the step of supplying the film substrate from a long winding body having a predetermined width and applying the resin composition constituting the alignment film on one surface of the film substrate.
The film base material constituting the wound body has a coefficient of variation of 1.3% or more in the thickness distribution in the width direction,
The phase difference is characterized in that the wound body is moisture-proof packaged by a moisture-proof film having a water vapor permeability of 0.1 g / m ² · day or less at 40 ° C. and 90% until immediately before the alignment film forming step. A method for producing a film.   The method for producing a retardation film according to claim 1, wherein the film substrate has an average thickness of less than 50 μm.

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