JP2014089355A - Polarizing light irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing light irradiation device that can attain a high polarization extinction ratio, a flat polarization azimuth and a wide irradiation area.SOLUTION: The polarizing light irradiation device has: a light source part 10 that discharges ultraviolet light; a parallel light formation part 20 that converges the ultraviolet light; and a polarizing light formation part 30. The polarizing light formation part 30 includes a plate type polarization beam splitter having a dielectric multi-layer film 32b provided on a first surface of a transparent plate 32a, and reflects a polarization component s of the ultraviolet light discharged from the parallel light formation part 20 and obliquely incident upon a surface of the dielectric multi-layer film 32b, transmits a polarization component p, and thereby discharges the split polarization component s as an irradiation beam.

Description

  Embodiments described herein relate generally to a polarized light irradiation apparatus.

  An alignment film for a liquid crystal panel can be photo-aligned by irradiating the surface of a thin film such as polyimide resin with linearly polarized light having an ultraviolet wavelength.

  As the liquid crystal panel is increased in definition and size, a polarized light irradiation device for a photo-alignment film is required to have a high polarization extinction ratio, a uniform polarization azimuth, and a large irradiation area.

  For example, to obtain transmitted light having a polarization extinction ratio of 100: 1 or more using a polarizer having a transparent plate with a refractive index of 1.6, the number of transparent plates to be laminated is 200 or more, and the apparatus is large. It becomes.

  In addition, in order to obtain light linearly polarized along the longitudinal direction of the rectangular irradiation region over a large area, it is necessary to incline the transparent plate in the longitudinal direction in a pile type polarizer in which a large number of transparent plates are stacked. For this reason, it is necessary to suppress the leakage of non-polarized light from the boundary region.

Japanese Patent No. 3146998

  Provided is a polarized light irradiation apparatus capable of a high polarization extinction ratio, a uniform polarization orientation, and a wide irradiation area.

  The polarized light irradiation apparatus according to the embodiment includes a light source unit that emits ultraviolet light, a parallel light forming unit that collects the ultraviolet light, and a polarized light forming unit. The polarized light forming unit includes a plate-type polarizing beam splitter having a dielectric multilayer film provided on a first surface of a transparent plate, and is emitted from the parallel light forming unit and is oblique to the surface of the dielectric multilayer film. By reflecting the s-polarized component of the incident ultraviolet light and transmitting the p-polarized component, the separated s-polarized component is emitted as an irradiation beam.

  Provided is a polarized light irradiation apparatus capable of a high polarization extinction ratio, a uniform polarization orientation, and a wide irradiation area.

It is a block diagram of the polarized light irradiation apparatus concerning the 1st Embodiment of this invention. It is a block diagram of the polarized light irradiation apparatus concerning the 2nd Embodiment of this invention. It is a block diagram of the polarized light irradiation apparatus concerning the 3rd Embodiment of this invention. It is a schematic diagram explaining a polarized light formation part. It is a schematic diagram explaining the reflection of p polarization | polarized-light and s-polarized light which entered into the interface of two media which have a different refractive index. FIG. 6A is a graph of the dependency on the amplitude reflectance, and FIG. 6B is a graph of the dependency on the amplitude reflectance of the p- and s-polarized light with respect to the incident angle. It is a model perspective view of the polarizer used for the polarized light irradiation apparatus concerning a 1st comparative example. FIG. 8A is a schematic perspective view of a polarized light forming unit in which plate-type polarization beam splitters used in the first to third embodiments are closely arranged. FIG. 9A is a schematic perspective view of a plate-type polarizing beam splitter according to a second comparative example, and FIG. 9B is a schematic perspective view in which a plurality of them are arranged. 10A is a schematic plan view of a modified example of the plate-type polarizing beam splitter used in the first to third embodiments, FIG. 10B is a schematic front view, and FIG. 10C is a CC line. FIG. 10D is a schematic cross-sectional view in which a dielectric multilayer film is partially enlarged. FIG. 11A shows an arrangement example of the plate-type polarization beam splitter, and FIG. 11B shows a modification thereof. It is a block diagram of the polarized light irradiation apparatus concerning 4th Embodiment. FIG. 13A is a schematic plan view of a polarized light irradiation apparatus according to the fifth embodiment, and FIG. 13B is a schematic cross-sectional view. It is a block diagram of the polarized light irradiation apparatus concerning 6th Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a polarized light irradiation apparatus according to the first embodiment of the present invention.
The polarized light irradiation device includes a light source unit 10, a parallel light forming unit 20, and a polarized light forming unit 30. The light source unit 10 includes an ultraviolet lamp 12 and a condenser mirror 14. The polarized light forming unit 30 includes a plate-type polarizing beam splitter 32, separates the ultraviolet light emitted from the parallel light forming unit 20 into a p-polarized component and an s-polarized component, and emits the s-polarized component as an irradiation beam. In the specification, the wavelength of “ultraviolet light” is 390 nm or less and includes deep ultraviolet light.

  The parallel light forming unit 20 has an optical axis 24, and converts ultraviolet light into parallel light around the optical axis 24 and obliquely enters the plate-type polarizing beam splitter 32. The parallel light forming unit 20 has a spread of ultraviolet light that is perpendicular to the surface of the dielectric multilayer film 32 b on the surface of the plate-type polarization beam splitter 32 and includes the optical axis 24 plus or minus 5 with respect to the optical axis 24. It is preferable to make the light collimated within a degree. Further, it is more preferable that the parallel light forming unit 20 makes the spread of the ultraviolet light substantially zero (that is, substantially parallel). In addition, you may further provide the condensing optical part which condenses the light of the light source part 10 between the light source part 10 and the parallel light formation part 20. FIG.

  The polarized light irradiation device may include an epi-illuminator 40 that reflects the s-polarized component emitted from the polarized light forming unit 30 toward the irradiation region 50. The irradiation area 50 is the surface of the irradiated object arranged on the transport unit 54. The irradiated body can be, for example, an alignment film 52 provided on the surface of the transparent substrate and made of resin or the like. The alignment film 52 becomes a photo-alignment film along a predetermined polarization direction when irradiated with linearly polarized light. Such a photo-alignment film can be used for a liquid crystal panel, a viewing angle compensation film, and the like.

  In addition, the polarized light irradiation apparatus can further include a transport unit 54 that moves the alignment film 52 continuously or intermittently along a straight line. If it does in this way, a photo-alignment film can be manufactured with high productivity by making the irradiation area | region 50 into a rectangle and making the longitudinal direction into a linearly polarized light direction, for example.

FIG. 2 is a configuration diagram of a polarized light irradiation apparatus according to the second embodiment of the present invention.
The polarized light irradiation device includes a light source unit 10, a parallel light forming unit 20, and a polarized light forming unit 30. The polarized light forming unit 30 includes a plate-type polarizing beam splitter 32 and a wire grid polarizing plate 33. The ultraviolet light emitted from the parallel-light forming unit 20 by the plate-type polarizing beam splitter 32 is converted into a p-polarized component and an s-polarized light. Further, the s-polarized light component separated by the plate-type polarization beam splitter 32 by the wire grid polarizing plate 33 is incident / transmitted and emitted as an irradiation beam. The wire grid type polarizing plate 33 is, for example, a polarizing element in which metal wires made of aluminum are provided at equal intervals and in parallel on the surface of a quartz plate.

FIG. 3 is a configuration diagram of a polarized light irradiation apparatus according to the third embodiment of the present invention.
The polarized light irradiation device includes a light source unit 10, a parallel light forming unit 20, and a polarized light forming unit 30. The polarized light forming unit 30 includes two plate-type polarizing beam splitters 32 and 34, separates the ultraviolet light emitted from the parallel light forming unit 20 into a p-polarized component and an s-polarized component, and irradiates the s-polarized component with an irradiation beam. To release as.

FIG. 4 is a schematic diagram illustrating a polarized light forming unit according to the third embodiment.
The polarized light forming unit 30 includes, for example, a first plate type polarization beam splitter 32 and a second plate type polarization beam splitter 34. The first plate-type polarization beam splitter 32 includes a transparent plate 32a and a dielectric multilayer film 32b that is provided on the first surface of the transparent plate 32a and includes at least two kinds of dielectrics having different refractive indexes.

  The second plate-type polarization beam splitter 34 includes a transparent plate 34a and a dielectric multilayer film 34b that is provided on the first surface of the transparent plate 34a and includes at least two types of dielectrics having different refractive indexes. If the first and second plate-type polarization beam splitters 32 and 34 have the same shape and material, the material efficiency can be improved. The material of the transparent plates 32 and 34 can be synthetic quartz or the like. In addition, although the transparent plates 32 and 34 are represented as wedge-shaped cross sections, the upper surface and the lower surface may be parallel.

  In FIG. 4, it is assumed that three homologous light beams, which are light beams forming a common wavefront, of ultraviolet light are represented. Of the homologous beams G1, G2, and G3 incident on the first polarizing beam splitter 32, rays passing through the center of the diaphragm 22 of the parallel light forming unit 30 are called principal rays, and are represented by g1, g2, and g3, respectively. The spread of the principal rays g1, g2, and g3 is preferably within plus or minus 5 degrees with respect to the optical axis 24 of the parallel light forming unit 30 in the section of the irradiation beam, and is parallel (no spread). More preferred.

  A part of the dielectric multilayer film 32b of the first plate-type polarizing beam splitter 32 and a part of the dielectric multilayer film 34b of the second plate-type polarizing beam splitter 34 are arranged so as to have regions facing each other. The The principal rays g1, g2, and g3 of the ultraviolet light emitted from the parallel light forming unit 20 are obliquely incident on the first polarizing beam splitter 32 (incident angle θ). The transmitted light is emitted from the back surface of the transparent plate 32a. On the other hand, the reflected light is incident on the second plate-type polarization beam splitter 34 obliquely. Also in this case, the transmitted light is emitted from the back surface of the transparent plate 34a, and the reflected light is emitted from the polarized light forming unit 30 as an irradiation beam. The homologous luminous flux emitted from the second polarization beam splitter 34 is denoted by G11, G12, and G13. For example, if the surface of the dielectric multilayer film 32b of the first polarization beam splitter 32 and the surface of the dielectric multilayer film 34b of the second polarization beam splitter 34 are substantially parallel, the irradiation beam can be efficiently emitted by oblique incidence. It can be taken out.

FIG. 5 is a schematic diagram for explaining the reflection of p-polarized light and s-polarized light incident on the boundary surface between two dielectric media having different refractive indexes.
It is assumed that the medium 1 has a refractive index n1, and the medium 2 has a refractive index n2. Incident light enters the boundary surface S1, resulting from reflected light and transmitted light. A surface that includes incident light, reflected light, and transmitted light and is perpendicular to the boundary surface S1 is denoted as S2. Further, the electric field vector of the incident light exists in a plane orthogonal to the traveling direction of the incident light, and can be decomposed into two electric field vectors orthogonal to each other. In particular, the former is referred to as a p-polarized component and the latter is referred to as an s-polarized component because it is convenient to decompose the component into a component perpendicular to the incident surface S2 and a component perpendicular thereto.

  In this case, the amplitude reflectance rp and the amplitude transmittance tp of the p-polarized component, and the amplitude reflectance rs and the amplitude transmittance ts of the s-polarized component can be expressed by Fresnel formulas of Equations (1) to (4). it can.

The Fresnel formulas in equations (1) to (4) indicate that the s-polarized amplitude reflectance rs is always higher than the p-polarized amplitude reflectance rp. As a result, the reflected light is biased to s-polarized light and the transmitted light is biased to p-polarized light. Further, when the numerator of the formula (1) becomes zero, the amplitude reflectance rp of the p-polarized light can be made substantially zero (the amplitude transmittance tp is about 100%), but this incident angle is called a Brewster angle.
Further, the relationship between the incident angle θ2 and the refraction angle θ1 is expressed by the Snell equation of equation (5).

FIG. 6A is a graph showing the dependence of the plate-type polarizing beam splitter on the amplitude reflectivity with respect to the wavelength of the ultraviolet light in the first embodiment, and FIG. 6B is the dependence of the incident angle on the amplitude reflectance of p and s-polarized light. FIG.
In FIG. 6A, the vertical axis represents amplitude reflectance (%), and the horizontal axis represents wavelength (nm). The refractive index of the transparent plate is 1.6, and the amplitude reflectivity per stage of the plate-type polarizing beam splitter is represented.

  In the dielectric multilayer structure, the effective refractive index of p-polarized light and the effective refractive index of s-polarized light at oblique incidence are different. By using simulation or the like, it is possible to determine the optimum values of the respective materials and film thicknesses constituting the multilayer film for the desired reflectance in the desired ultraviolet light wavelength region. For example, as shown in FIG. 5A, at a wavelength of 254 nm, the s-polarization amplitude reflectance can be 96% or more, and the polarization extinction ratio can be 20: 1 or more.

  In FIG. 6B, the vertical axis represents the amplitude reflectance (%), and the horizontal axis represents the incident angle (degrees). An angle formed by the optical axis 24 of the parallel light forming unit 20 and the normal line of the surface of the dielectric multilayer film 32b is defined as an incident angle θ. When the incident angle is 70 ± 5 degrees, the amplitude reflectance of s-polarized light can be 96% or more, and the polarization extinction ratio can be 20: 1 or more. According to the experiments by the inventors, when a dielectric made of Si compound or metal oxide and transparent to ultraviolet light is used, it is shown in FIGS. 4A and 4B regardless of the material. It has been found that reflection characteristics can be obtained.

  In the second embodiment, since two plate-type polarization beam splitters are provided, two or more reflections can be generated. For this reason, the polarization extinction ratio can be increased to 400: 1 or more. If the reflection is performed three times, the polarization extinction ratio can be 8000: 1 or more. Further, since the s-polarized component does not pass through the transparent plates 32a and 34a, elliptically polarized light can be suppressed by the stress birefringence in the plate-type polarizing beam splitter. For this reason, the polarization extinction ratio can be kept high.

FIG. 7 is a schematic perspective view of a polarizer used in the polarized light irradiation apparatus according to the first comparative example.
The polarizer in the comparative example is a pile-type polarizer in which a plurality of transparent plates 100 are stacked in parallel at intervals to increase the bias of transmitted light to p-polarized light. The polarization extinction ratio (ER: 1) of the pile type polarizer can be expressed by Equation (6) where m is the number of plates and n is the refractive index of the plates.

  For example, if the refractive index of the transparent plate 100 is 1.6, 208 transparent plates 100 are required to obtain a polarization extinction ratio of 100: 1. If the refractive index of the transparent plate 100 is 1.8, 128 transparent plates 100 are required to obtain a polarization extinction ratio of 100: 1. For example, if the thickness of the transparent plate 100 is 1 mm and the interval is 100 μm, the total thickness of the pile-type polarizer increases to 23 cm or more and 14 cm or more, respectively. In addition, the polarization extinction ratio may decrease due to elliptically polarized light generated in the transparent plate 100.

  On the other hand, in the third embodiment, since the reflection of the s-polarized component is repeated, it is possible to suppress a decrease in the polarization extinction ratio due to elliptically polarized light.

FIG. 8 is a schematic perspective view of a polarized light forming unit in which plate-type polarization beam splitters used in the first to third embodiments are closely arranged.
The plate-type polarizing beam splitter 60 irradiates the irradiation region 50 with the separated s-polarized component of the non-polarized light 62. For this reason, the irradiation region 50 can be expanded along the polarization direction of the s-polarized light. For example, by continuously or intermittently transporting the alignment film in the transport direction, the alignment film can be irradiated with an s-polarized beam to form a photo-alignment film. However, it is difficult to increase the size of one dielectric multilayer film.

  That is, the dielectric multilayer film needs to be laminated with a film having high thickness accuracy. In the vacuum vapor deposition apparatus, since the film thickness distribution is concentric, the polarization characteristics are distributed concentrically. In order to reduce the characteristic distribution, it is preferable to arrange large-area multilayer films having small and uniform characteristics in parallel. In this way, the polarization orientation can be made uniform at 0.01 degrees or less over the plane of the irradiation region 50.

  In this case, strong non-polarized light 62 is incident on the gap region of the plate-type polarizing beam splitter 60. However, the non-polarized light 62 does not irradiate the irradiation region 50 because it passes through the transparent plate.

FIG. 9A is a schematic perspective view of a polarizing beam splitter according to a second comparative example, and FIG. 9B is a schematic perspective view in which a plurality of these are arranged.
In the second comparative example, the polarization beam splitter is a wire grid polarizer (WGP). The WGP has a substrate 160a and fine metal wires 160a provided on the surface thereof. The polarized light component parallel to the metal thin wire 160a is reflected, and the polarized light component orthogonal thereto is transmitted to separate the polarized light.

  Since the surface of WGP is covered with a metal in an area of about 50%, the transmittance (referred to as polarized transmittance) when irradiated with polarized light in the same direction as the transmitted polarized light is far from 100%. It doesn't reach. Further, the polarization extinction ratio can be increased as the pitch D of the wire grid is reduced, but in the deep ultraviolet region, several ten: 1 is the limit. If an attempt is made to increase the polarization extinction ratio, the polarization transmittance decreases, so that it is not effective to increase the number of stages. Further, in the deep ultraviolet region, the metal thin wire may be oxidized due to high energy, and the polarization extinction ratio may decrease.

When arranging a plurality of polarization beam splitters made of WGP as shown in FIG.
Unpolarized light 162 is transmitted from the gap region. For this reason, a region where a desired photo-alignment film cannot be formed may be generated. For this reason, for example, it is necessary to provide a light shielding band in the gap region. On the other hand, in the embodiment shown in FIG. 8, it is not necessary to provide a light shielding band. On the other hand, as shown in FIG. 2, if the s-polarized light component reflected and separated by the plate-type polarizing beam splitter is incident on and transmitted through the wire grid type polarizing plate, it is already non-exposed before entering the wire grid type polarizing plate. Since there is almost no polarized light, this embodiment can further increase the polarization extinction ratio without providing a light shielding band.

10A is a schematic plan view of a modified example of the plate-type polarizing beam splitter used in the first embodiment, FIG. 10B is a schematic front view, and FIG. 10C is a schematic view taken along the line CC. FIG. 10D is a schematic cross-sectional view in which the surface region SU of the dielectric multilayer film is partially enlarged.
As shown in FIG. 10A, the planar shape of the plate-type polarizing beam splitter can be a parallelogram. As shown in FIG. 10C, the upper surface and the lower surface can have a wedge-shaped cross section having a taper angle of about 5 degrees. By providing a taper of approximately 5 degrees, the unpolarized light 62 is incident at 70 degrees, and the reflected s-polarized light 63 is offset from the s-polarized light 65 incident on the transparent plate 60 and reflected on the back surface side by approximately 22 degrees. , Polarization separation can be performed at spaced positions on the surface. Further, all the ridges on the front side can be chamfered (C0.5) such as 0.5 mm in width.

As shown in FIG. 10D, the dielectric multilayer film 61 may include a protective film 61a on the surface. When the protective film 61a is made of, for example, SiO ₂ (refractive index: approximately 1.5), it is possible to suppress the deposition of organic substances or the like on the surface 61b by irradiation with high energy ultraviolet light. Furthermore, when the thickness of the protective film 61a is increased while maintaining the amplitude reflectance of the dielectric multilayer film 61, the surface 61b can be cleaned to stabilize the amplitude reflectance.

FIG. 11A shows an arrangement example of the plate-type polarization beam splitter, and FIG. 11B shows a modification thereof.
In FIG. 11A, four parallelogram plate-type polarizing beam splitters 70 whose surfaces are chamfered are arranged. Since the chamfer region 71 having a width of 1 mm, which is the boundary between the two plate-type polarization beam splitters 70, is inclined with respect to the transport direction of the irradiated object, the boundary region is also irradiated with the beam. Alternatively, the plate-type polarizing beam splitter 73 having a square shape or a rectangular shape may be shifted by being rotated.

FIG. 12 is a configuration diagram of a polarized light irradiation apparatus according to the fourth embodiment.
The light source unit 10 includes an ultra high pressure mercury lamp (short arc lamp) 12. The parallel light forming unit 20 combines, for example, an elliptical mirror 90, a relay lens 91 composed of a plurality of plano-convex and biconvex lenses, a fly-eye lens (integrator) 92, a plane mirror 93, a spherical mirror 94, and the like to convert ultraviolet light into parallel light. Turn into. The collimated ultraviolet light is represented by homologous light beams G1, G2, G3, G11, G12, and G13. The spread of the chief rays g 1, g 2, g 3, g 11, g 12, and g 13 in the beam cross section of the same-family light beam is preferably within plus or minus 5 degrees with respect to the optical axis 24 of the parallel light forming unit 20. (Telecentric optical system) is more preferable.

FIG. 13A is a schematic plan view of a polarized light irradiation apparatus according to the fifth embodiment, and FIG. 13B is a schematic cross-sectional view taken along a line.
The light source unit 10 includes a rod-shaped light source unit (long arc lamp) 13 such as a high-pressure mercury lamp. The parallel light forming unit 20 includes two slits 95 that shield unnecessary light beams from the light source unit 10, and a cylinder lens 96 that uses principal rays g1, g2, and g3 of emitted light from the slits 95 as parallel light. The chief rays g11, g12, and g13 of the irradiation beam from the polarized light irradiation device can be made parallel.

FIG. 14 is a configuration diagram of a polarized light irradiation apparatus according to the sixth embodiment.
If three or more plate-type polarizing beam splitters are arranged and reflected three or more times, the polarization extinction ratio can be further increased. In this case, the principal ray of incident light preferably has a small divergence angle and is close to parallel light. In particular, in the deep ultraviolet wavelength region of 254 to 313 nm, it is preferable that the incident angle change width is as narrow as about 10 degrees or less. Also, in this wavelength range, as in the case of visible light, a sufficient polarization extinction ratio cannot be obtained when the incident angle is around 45 degrees, and it is preferable that the incident angle be around 70 degrees.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 Light source part, 20 Parallel light formation part, 24 Optical axis (of parallel light formation part), 30 Polarization light formation part, 32, 34, 36, 70, 73 Plate type polarization beam splitter, 32a, 34a Transparent plate, 32b, 34b Dielectric multilayer film, 33 Wire grid type polarizing plate, 52 Alignment film, 54 Transport section, 95 slit, 91, 92, 96 Lens, G1, G2, G3

Claims (7)

A light source that emits ultraviolet light;
A collimated light forming unit that collects the ultraviolet light; and
A plate-type polarizing beam splitter having a dielectric multilayer film provided on the first surface of the transparent plate, the ultraviolet light emitted from the parallel light forming portion and obliquely incident on the surface of the dielectric multilayer film; A polarized light forming unit that emits the separated s-polarized light component as an irradiation beam by reflecting the s-polarized light component and transmitting the p-polarized light component,
A polarized light irradiation apparatus.   The polarized light irradiation apparatus according to claim 1, wherein the polarized light forming unit further includes a wire grid type polarizing plate, and the ultraviolet light reflected by the plate type polarization beam splitter is incident and emitted as an irradiation beam. The polarized light forming unit includes first and second plate-type polarization beam splitters,
A part of the dielectric multilayer film of the first plate-type polarizing beam splitter and a part of the second plate-type dielectric multilayer film are opposed to each other,
The ultraviolet light emitted from the parallel light forming unit is incident on the surface of the dielectric multilayer film of the first plate-type polarizing beam splitter,
The s-polarized light reflected by the dielectric multilayer film of the first plate-type polarization beam splitter is incident on the surface of the dielectric multilayer film of the second plate-type polarization beam splitter,
The polarized light irradiation apparatus according to claim 1, wherein the s-polarized light reflected by the dielectric multilayer film of the second plate-type polarizing beam splitter is used as the irradiation beam.   4. The optical axis of the parallel light forming unit is 70 ± 5 degrees with respect to a normal of the surface of the dielectric multilayer film of the first polarizing beam splitter. Polarized light irradiation device.   5. The polarized light irradiation apparatus according to claim 3, wherein the surface of the dielectric multilayer film of the first plate-type polarizing beam splitter is parallel to the surface of the second plate-type dielectric multilayer film. .   The polarized light irradiation apparatus according to claim 1, wherein a planar shape of the dielectric multilayer film is a parallelogram.   The polarized light irradiation apparatus according to claim 1, wherein a cross section of the transparent plate has a wedge shape.

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