JP2018072567A - Electromagnetic wave irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave irradiation device that features high optical energy utilization efficiency and low heat generation.SOLUTION: An electromagnetic wave irradiation device 100 consists of; a light source 1 for emitting an electromagnetic wave; a curved mirror 2 configured to reflect the electromagnetic wave emitted by the light source 1 toward a target object 200; a polarizer 3 configured to transmit polarized light A, of the electromagnetic wave, having a polarization axis parallel to a predetermined reference direction and to reflect polarized light B having a polarization axis perpendicular to the reference direction; and a retardation element 4 disposed between the mirror 2 and the polarizer 3 and configured to convert the polarized light B into circularly or elliptically polarized light.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electromagnetic wave irradiation device.

  Conventionally, a rubbing method is known as an alignment treatment for an alignment film of a liquid crystal panel. The rubbing method is a method of rubbing the surface of the alignment film in a certain direction by rotating a roller wound with a cloth such as nylon against the substrate coated with the alignment film while pressing it with a certain pressure. However, the rubbing method generates particles and static electricity due to friction between the roller and the surface of the polymer film, and thus has been a factor affecting the yield and the like.

  In recent years, therefore, a photo-alignment technique (see, for example, Patent Document 1 and Patent Document 2) has been used as a technique that replaces the rubbing process. The ultraviolet irradiation device used in this photo-alignment technique is mainly composed of a rod-shaped straight tube lamp as a light source and a polarizer. Then, the alignment film is subjected to an alignment process by allowing the polarizer to pass ultraviolet rays having a polarization axis in a predetermined direction among the ultraviolet rays irradiated by the straight tube lamp, and irradiating the target with the passed ultraviolet rays.

JP 2009-265290 A JP2011-145381

  However, since the conventional ultraviolet irradiation device uses only ultraviolet rays having a polarization axis in a predetermined direction by a polarizer, there is a problem that the utilization efficiency of light energy is low. Further, since the light energy that could not be used is changed to heat, there is a problem that the life of the ultraviolet irradiation device is shortened by the heat.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electromagnetic wave irradiation apparatus that has high utilization efficiency of light energy and low heat generation.

  In order to achieve the above object, an electromagnetic wave irradiation device of the present invention includes a light source that emits an electromagnetic wave, a curved mirror that reflects the electromagnetic wave emitted from the light source toward an object, and a predetermined one of the electromagnetic waves. A polarizer that transmits the polarized light A having a polarization axis parallel to the reference direction and reflects the polarized light B having a polarization axis perpendicular to the reference direction, and is disposed between the mirror and the polarizer. And a phase difference element that converts the light into circularly polarized light or elliptically polarized light.

  The mirror may have a parabolic or elliptical cross section. In this case, the retardation element reflects 50% or more of the electromagnetic wave reflected by the polarizer and passed through the retardation element, preferably 75% or more, more preferably 90% or more by one reflection by the mirror. It is better to arrange so as to pass through the phase difference element. More preferably, the phase difference element should be arranged at the focal point of the mirror.

  In addition, when the cross section of the mirror is elliptical, it is preferable that the polarizer is disposed closer to the center than the two focal points of the ellipse.

  Further, the mirror made of metal can be used.

  In addition, it is preferable that the retardation element has an ellipticity of electromagnetic waves of 0.7 or more when linearly polarized electromagnetic waves are transmitted.

  Since the electromagnetic wave irradiation apparatus of the present invention changes the polarization axis of the electromagnetic wave reflected by the polarizer and transmits the polarizer, the utilization efficiency of light energy can be increased. Moreover, since generation | occurrence | production of a heat | fever can be suppressed, the lifetime of an electromagnetic wave irradiation apparatus can be lengthened.

It is a schematic sectional drawing which shows the electromagnetic wave irradiation apparatus of this invention. It is a schematic sectional drawing which shows another electromagnetic wave irradiation apparatus of this invention. It is (a) schematic perspective view and (b) schematic sectional drawing for demonstrating the electromagnetic wave irradiation apparatus of the simulation 1. FIG. It is (a) schematic perspective view and (b) schematic sectional drawing for demonstrating the electromagnetic wave irradiation apparatus of the simulation 2. FIG. It is (a) schematic perspective view and (b) schematic sectional drawing for demonstrating the electromagnetic wave irradiation apparatus of the simulation 3. FIG.

  Below, the electromagnetic wave irradiation apparatus of this invention is demonstrated. As shown in FIG. 1, the electromagnetic wave irradiation apparatus 100 of the present invention mainly includes a light source 1, a mirror 2, a polarizer 3, and a phase difference element 4.

  First, the principle of the electromagnetic wave irradiation apparatus 100 of this invention is demonstrated using FIG.

  The electromagnetic wave X emitted from the light source 1 is transmitted by the polarizer 3 with the polarization A having a polarization axis parallel to a predetermined reference direction and the polarization B having a polarization axis perpendicular to the reference direction. The transmitted polarized light A is applied to the object 200. On the other hand, the reflected polarized light B is converted to circularly polarized (or elliptically polarized) electromagnetic wave β when passing through the phase difference element 4. Subsequently, when the electromagnetic wave β is reflected by the mirror 2, the electromagnetic wave α becomes circularly polarized light (or elliptically polarized light) that is reversely rotated from that before the reflection. When the electromagnetic wave α passes through the phase difference element 4 again, the electromagnetic wave β is reversely rotated with respect to the electromagnetic wave β before being reflected by the mirror 2, so that the polarized light B becomes linearly polarized light having a different polarization axis angle. This electromagnetic wave is again transmitted by the polarizer 3 through the polarized light A and the polarized light B is reflected. By repeating this, the electromagnetic wave irradiated from the light source 1 can be efficiently extracted as the polarized light A. In particular, when the phase difference imparted to the electromagnetic wave by the phase difference element 4 is ¼ wavelength, once the electromagnetic wave is re-passed through the phase difference element 4 by the mirror 2 as shown in FIG. The electromagnetic wave can be substantially converted into polarized light A and transmitted through the polarizer 3. Therefore, loss due to absorption can be minimized.

  Next, each component of the electromagnetic wave irradiation apparatus 100 of the present invention will be described.

  The light source 1 is for emitting electromagnetic waves. The electromagnetic wave may be selected according to the application, and examples thereof include ultraviolet rays, visible rays, infrared rays, and the like. The light source 1 may emit only an electromagnetic wave having a specific wavelength, but may emit an electromagnetic wave having a wavelength in a predetermined range including an electromagnetic wave having a specific wavelength according to the application. In this case, only the target electromagnetic wave may be separated by a filter that transmits only the electromagnetic wave having a specific wavelength. In the case of an ultraviolet irradiation device used for alignment treatment of an alignment film of a liquid crystal panel, for example, a mercury lamp in which a rare gas such as mercury, argon, or xenon is sealed in an ultraviolet transmissive glass tube, or an iron or iodine in a mercury lamp A metal halide lamp in which a metal halide such as is further enclosed can be used as the light source.

  The mirror 2 is formed in a curved surface so that the inner surface includes the light source 1, and reflects the electromagnetic wave toward the polarizer 3. As the material of the mirror 2, any material can be used as long as the rotation direction of the electromagnetic wave of circularly polarized light (or elliptically polarized light) can be reversed from that before the reflection by reflection. For example, aluminum (Al) or silver A metal such as (Ag) can be used. Further, the shape of the mirror 2 is an elliptical section that can condense the electromagnetic wave emitted from the light source 1 onto the object 200, or a parabolic one that can condense the electromagnetic wave emitted from the light source 1 parallel to the object 200. Can be used. In this case, the light source 1 should just be arrange | positioned in the position of the focus of an ellipse or a parabola. Note that the shape of the mirror 2 is not limited to these as long as the object 200 can be irradiated with electromagnetic waves emitted from the light source 1. Further, the electromagnetic wave irradiation device 100 can be combined with a lens capable of condensing the electromagnetic wave emitted from the light source 1 at a specific position.

  The polarizer 3 transmits polarized light A having a polarization axis parallel to a predetermined reference direction among electromagnetic waves and reflects polarized light B having a polarization axis perpendicular to the reference direction. Any polarizer 3 may be used as long as it is a so-called reflective polarizer 3. For example, it is possible to use a reflective wire grid having convex portions formed in a line-and-space manner in parallel with each other on the surface of the base portion. As the material of the convex portion, for example, a metal or metal oxide such as aluminum (Al), silver (Ag), or amorphous silicon can be used. The convex portion may have a multilayer structure made of a plurality of materials. The base material may be any material as long as it can transmit polarized light A, and glass, transparent resin, or the like can be used. In the case of an ultraviolet irradiation device used for alignment treatment of an alignment film of a liquid crystal panel, quartz glass is suitable as a base material in consideration of heat resistance and transparency. The polarizer 3 may be one in which the base dielectric is filled between the convex portions, or the convex portion may be included in the base portion. Thereby, intensity | strength can be raised or corrosion of a metal wire can be prevented.

  In addition, the polarizer 3 is more preferable in that the higher the extinction ratio is obtained over a wider wavelength range, in particular, the shorter wavelength range, the narrower the pitch of the convex portions and the higher the aspect ratio.

  When the cross section of the mirror 2 is elliptical, the polarizer 3 is preferably arranged closer to the center than the two focal points of the ellipse, and preferably half the distance from the center of the ellipse to one of the focal points. It is preferable that the lens is disposed within the center of the focal point.

  The phase difference element 4 is disposed between the mirror 2 and the polarizer 3 and converts the polarized light B into circularly polarized light or elliptically polarized light. As described above in the description of the principle, it is preferable that the phase difference element 4 provides a quarter wavelength phase difference to the transmitted electromagnetic wave. However, when the phase difference element 4 has an uneven structure, it may be difficult to process the phase difference element 4 depending on the aspect ratio. Therefore, the phase difference provided by the phase difference element 4 may be set to ¼n wavelength (n is a natural number of 2 or more). In this case, in order to convert all the electromagnetic waves into the polarized light A, the number of times of re-irradiation to the phase difference element 4 by the mirror 2 is required n times. Compared with the concavo-convex structure giving a quarter wavelength, it can be reduced to 1 / n, and processing becomes easy. For example, if the phase difference provided by the phase difference element 4 is 1/8 wavelength, the number of times of re-irradiation to the phase difference element 4 by the mirror 2 is required twice, but the aspect ratio of the concavo-convex structure is the phase difference. The concavo-convex structure giving a quarter wavelength can be halved. In addition, the error of the phase difference provided by the phase difference element 4 is preferably ± 10% or less, more preferably 5% or less, with respect to the quarter wavelength or the quarter wavelength.

  In addition, as shown in FIG. 2, when the position of the phase difference element 4 is close to the opening 21 side of the mirror 2, the electromagnetic wave β that has passed through the phase difference element 4 passes through the phase difference element 4 again before the mirror 2. Will be reflected twice. In this case, since the rotation of the electromagnetic wave returns to the original, the electromagnetic wave that has passed through the phase difference element 4 returns to the original polarized light B, and hardly passes through the polarizer 3. That is, when the electromagnetic wave passes through the phase difference element 4 again, in order to reverse the rotation direction of the electromagnetic wave to that before the reflection, the mirror from passing through the phase difference element 4 to passing through the phase difference element 4 again. It is necessary to make the reflection by 2 an odd number of times. Accordingly, 50% or more, preferably 75% or more, more preferably 90% or more of the electromagnetic wave reflected by the polarizer 3 and passed through the phase difference element 4 passes through the phase difference element 4 again by one reflection by the mirror 2. Thus, the phase difference element 4 is preferably arranged. For example, when the cross section of the mirror 2 is elliptical or parabolic, the phase difference element 4 is preferably arranged at the focal point of the ellipse or parabola or as close to the focal point as possible. . Thereby, after passing through the phase difference element 4 and before passing through the phase difference element 4 again, the number of times the electromagnetic wave is reflected by the mirror 2 can be reduced to one.

  As a characteristic of the phase difference element 4, the ellipticity after conversion is 0.6 or more, preferably 0.7 or more.

As such a phase difference element 4, any element can be used as long as it can convert the polarized light B into circularly polarized light or elliptically polarized light. For example, an element having a concavo-convex structure and giving a phase difference to an electromagnetic wave passing through the structure. Can be used. The concavo-convex structure is formed, for example, in a line and space shape having convex portions and concave portions having a width smaller than the wavelength λ. Further, the concavo-convex structure may be formed integrally with the same material as the base, or may be formed with a material different from the base. As a material used for the convex part of the concavo-convex structure, inorganic compounds such as quartz and non-alkali glass, metals such as silver, gold, aluminum, nickel and copper, silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ) Such metal oxides and resins can be used. In addition, the material is preferably one in which electrons are not excited by an electromagnetic wave having a wavelength λ, and corresponds to a metal oxide such as silicon dioxide (SiO ₂ ) or aluminum oxide (Al ₂ O ₃ ).

  Next, the effect of the electromagnetic wave irradiation apparatus of the present invention will be described using simulation. For the simulation, the software DiffractMOD and LightTools manufactured by synopsys, Inc. were used.

[Simulation 1]
First, a simulation was performed for a case where the cross section of the mirror is elliptical. A model of the electromagnetic wave irradiation apparatus used for the simulation will be described with reference to FIG.

  The light source 1 was a cylinder having a diameter of 5 mm and a length of 500 mm, and the wavelength of the emitted electromagnetic wave was 254 nm.

  As shown in FIG. 3A, the mirror 2 has a shape that includes the light source 1, and has a shape in which a part of an ellipse is continued by 500 mm in the longitudinal direction of the light source 1. As shown in FIG. 3B, the ellipse has a shape obtained by cutting an ellipse having a distance between two focal points of 241 mm and a vertex-to-focal distance of 21.1 mm in the minor axis direction of the ellipse. The size of the cut opening 21 was 145 mm. The light source 1 was disposed at a focal position included in the ellipse. The material of the mirror 2 was aluminum.

The polarizer 3 has a pitch of 100 nm, a height of a convex portion of 180 nm, a width of the convex portion of 30 nm or 40 nm, and a material of the convex portion made of amorphous silicon or aluminum on a silicon dioxide (SiO ₂ ) substrate. A kind of wire grid. Further, the position of the polarizer was arranged in parallel with the opening 21 of the mirror at the position of the focal point on the non-encapsulated side of the ellipse constituting the mirror described above.

  The phase difference element provided a phase difference of ¼ wavelength to the electromagnetic wave passing therethrough was arranged in parallel with the mirror opening 21 with a gap of 0.5 mm from the light source 1.

  About these, the light reception amount which is ratio of the light quantity which permeate | transmitted the polarizer 3 with respect to the light quantity which the light source 1 discharge | released was calculated. Further, the improvement rate due to the presence or absence of the phase difference element 4 was also calculated. The results are shown in Table 1.

  From Table 1, it can be seen that when the phase difference element 4 is disposed between the mirror 2 and the polarizer 3, the amount of received light is improved. It can also be seen that the light receiving amount of the convex material is higher in aluminum than in amorphous silicon.

[Simulation 2]
Next, as shown in FIG. 4, the position of the polarizer 3 in the simulation 1 is arranged at the center between the two focal points of the ellipse of the mirror 2. In this case, the same calculation as in simulation 1 was performed. The results are shown in Table 2.

From Table 2, it can be seen that the position of the polarizer 3 is higher in the amount of received light and the effect of the phase difference element is higher than the position of the polarizer 3 in the center of the ellipse constituting the mirror.
[Simulation 3]
Next, a simulation was performed for the case where the mirror had a parabolic cross section. A model of the electromagnetic wave irradiation apparatus used for the simulation will be described with reference to FIG.

  The light source 1 was a cylinder having a diameter of 5 mm and a length of 500 mm, and the wavelength of the emitted electromagnetic wave was 254 nm.

  As shown in FIG. 5A, the mirror 2 has a shape that includes the light source 1, and has a shape in which a parabola is continuous by 500 mm in the longitudinal direction of the light source 1. As shown in FIG. 5B, the parabola has a vertex-to-focal distance of 10.2 mm, and the size of the opening 21 is 124.5 mm. The light source 1 was placed at the focal point of this parabola. The material of the mirror 2 was aluminum.

The polarizer 3 has a pitch of 100 nm, a height of a convex portion of 180 nm, a width of the convex portion of 30 nm or 40 nm, and a material of the convex portion made of amorphous silicon or aluminum on a silicon dioxide (SiO ₂ ) substrate. A kind of wire grid. Moreover, the position of the polarizer was arrange | positioned in the opening part 21 of the parabola which comprises the mirror mentioned above.

  The phase difference element 4 provided a phase difference of ¼ wavelength to the electromagnetic wave passing therethrough was arranged in parallel with the opening 21 of the mirror with a gap of 0.5 mm from the light source 1.

  Table 3 shows the result of the light reception amount which is the ratio of the light amount transmitted through the polarizer 3 to the light amount emitted from the light source 1 and the improvement rate depending on the presence or absence of the phase difference element 4.

  From Table 3, it can be seen that when the phase difference element 4 is disposed between the mirror 2 and the polarizer 3, the amount of received light is improved. It can also be seen that the light receiving amount of the convex material is higher in aluminum than in amorphous silicon.

DESCRIPTION OF SYMBOLS 1 Light source 2 Mirror 3 Polarizer 4 Phase difference element
100 Electromagnetic wave irradiation device
200 Object A Linearly polarized light (electromagnetic wave)
B Linearly polarized light (electromagnetic wave)
X Electromagnetic wave α Electromagnetic wave β Electromagnetic wave

Claims (8)

A light source that emits electromagnetic waves;
A curved mirror that reflects the electromagnetic wave emitted from the light source toward an object;
A polarizer that transmits polarized light A having a polarization axis parallel to a predetermined reference direction out of the electromagnetic wave and reflects polarized light B having a polarization axis perpendicular to the reference direction;
A phase difference element that is disposed between the mirror and the polarizer and converts the polarized light B into circularly polarized light or elliptically polarized light;
An electromagnetic wave irradiation apparatus comprising:   The electromagnetic wave irradiation apparatus according to claim 1, wherein the mirror has an elliptical or parabolic cross section.   The phase difference element is arranged so that 50% or more of the electromagnetic wave reflected by the polarizer and passed through the phase difference element passes through the phase difference element again by one reflection by the mirror. The electromagnetic wave irradiation apparatus according to claim 1 or 2.   The phase difference element is arranged such that 90% or more of the electromagnetic wave reflected by the polarizer and passed through the phase difference element is again passed through the phase difference element by one reflection by the mirror. The electromagnetic wave irradiation apparatus according to claim 1 or 2. The electromagnetic wave irradiation apparatus according to claim 2, wherein the phase difference element is disposed at a focal position of the mirror. The mirror has an elliptical cross section,
The electromagnetic wave irradiation apparatus according to claim 1, wherein the polarizer is disposed closer to the center than the two focal points of the ellipse.   The electromagnetic wave irradiation apparatus according to claim 1, wherein the mirror is made of metal.   The electromagnetic wave irradiation apparatus according to claim 1, wherein the retardation element has an ellipticity of electromagnetic waves of 0.7 or more when linearly polarized electromagnetic waves are transmitted.

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