JP2006201273A - Polarized light irradiating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To irradiate an optical alignment layer in a light irradiation region with a polarized light being diffused light without causing fluctuations of the polarization axis, even if an optical element, through which light is transmitted or on which light is reflected, is arranged in its optical path in an apparatus for irradiating the optical alignment layer with the polarized light being a diffuse light. <P>SOLUTION: A work 30, on which the optical alignment layer 31 is formed, is mounted on a work stage 32, and the whole of the work stage 32 is housed in a sample chamber 1. Inert gas, such as gaseous nitrogen, is introduced into the sample chamber 1 or is degassed therefrom. A light transmissive window 3 is formed at an upper part of the sample chamber 1, light from a light irradiation section 20 is transmitted through the light transmissive window 3, is polarized by a wire grid polarizing element 10 provided between the light transmissive window 3 and the work stage and irradiates the optical alignment layer 31 on the work stage 32. Since the optical element for transmitting or reflecting light is not provided between the polarizing element 10 and the optical alignment layer 31, rotation of the axis of polarization will not be produced and the fluctuations of the axis of polarization will not be produced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarized light irradiation apparatus that performs optical alignment by irradiating polarized light to an alignment film such as an alignment film of a liquid crystal display element or an alignment layer of a viewing angle compensation film using an ultraviolet curable liquid crystal.

In recent years, with respect to alignment processing of alignment films of liquid crystal elements such as liquid crystal panels and alignment layers of viewing angle compensation films, alignment is performed by irradiating polarized light of a predetermined wavelength to the alignment film. Technology is being adopted. Hereinafter, films and layers in which alignment characteristics are generated by light, such as an alignment film that performs alignment by light and a film provided with an alignment layer, are collectively referred to as a photo-alignment film.
The photo-alignment film has been enlarged along with the enlargement of the liquid crystal panel, and the polarized light irradiation apparatus for irradiating the photo-alignment film with polarized light has also been enlarged. In the photo-alignment film, for example, a viewing angle compensation film is a long strip-shaped workpiece, and is used after being cut to a desired length after the alignment treatment. Recently, the size of the panel has increased to match the size of the panel, and some have a width of 1500 mm.
In recent years, in order to perform photo-alignment on such a long strip-shaped photo-alignment film, a light irradiation apparatus using a light-emitting lamp having a length corresponding to the width of the photo-alignment film as a light source is used. It has been proposed to carry out light irradiation while transporting in a direction perpendicular to the longitudinal direction (see, for example, Patent Document 1 and Patent Document 2).
A rod-shaped lamp having a relatively long length is conventionally manufactured, and a rod-shaped lamp having a length of, for example, 1500 mm described above corresponding to the width direction of the photo-alignment film can be manufactured. However, since the light emitted from the rod-shaped lamp is diffused light, it is necessary to select a polarizing element that efficiently polarizes the diffused light. In the above publication, a polarizing element called a wire grid polarizer is used as such a polarizing element. Has been.

Details of the wire grid polarization element are disclosed in, for example, Patent Document 3 and Patent Document 4. As shown in FIG. 5, the schematic structure is that a plurality of linear electric conductors 10a whose length is much longer than the width (for example, metal wires such as chromium and aluminum; hereinafter referred to as grids) are on the same plane ( For example, it is arranged in parallel on the substrate 10b such as quartz glass. When the polarizing element is inserted in the optical path, most of the polarized components parallel to the longitudinal direction of the grid are reflected and the orthogonal polarized components pass. Accordingly, the direction of the polarization axis of the irradiated polarized light is a direction orthogonal to the longitudinal direction of the grid of the polarizing element.
As a feature of the wire grid polarizing element, it is known that the dependency of the extinction ratio of polarized light on the incident angle (the angle of light incident on the polarizing element) is small.
In FIG. 6, the structural example of the polarized light irradiation apparatus which combined the rod-shaped lamp and the wire grid polarizing element is shown.
A light irradiation unit 20 including a rod-shaped lamp 21 such as a high-pressure mercury lamp or a metal halide lamp, and a bowl-shaped condensing mirror 22 having an elliptical cross section for reflecting the light from the lamp 21, and the longitudinal direction of the lamp 21 is a workpiece 30 It arrange | positions so that it may become the width direction (perpendicular direction with respect to a conveyance direction) of the photo-alignment film 31 formed on it. The light irradiation unit 20 is provided with a wire grid polarizing element 10. The wire grid polarizing element 10 has a rectangular shape with one side slightly longer than the light emission length of the lamp 21, and is provided such that its longitudinal direction coincides with the longitudinal direction of the lamp 21.

The rod-shaped lamp 21 is arranged so that its longitudinal direction coincides with the longitudinal direction of the bowl-shaped condenser mirror 22, and so that its cross section coincides with the first focal position of the elliptic bowl-shaped condenser mirror 22, The photo-alignment film 31 formed on the work 30 is disposed at the second focal position of the bowl-shaped condenser mirror 22.
The workpiece 30 is, for example, a long continuous workpiece, wound around the delivery roller R1 in a roll shape, drawn out from the delivery roller R1, conveyed, and taken up by the take-up roller R2 under the light irradiation unit 20. It is done.
When the work 30 is transported under the light irradiation unit 20, the light alignment film 31 of the work 30 is irradiated with light from the rod-shaped lamp 21 polarized by the wire grid polarizing element 10 to be subjected to a light alignment process.
In FIG. 6, the grid of the wire grid polarizing element 10 is provided in parallel to the longitudinal direction of the rod-shaped lamp 21. Therefore, the polarization axis of the polarized light irradiated to the photo-alignment film is the longitudinal direction of the rod-shaped lamp 21. The direction perpendicular to the direction, that is, the direction parallel to the transport direction of the photo-alignment film. If the length of the rod-shaped lamp 21 is provided corresponding to the width of the photo-alignment film and the photo-alignment film is moved in one direction relative to the polarized light irradiation device, in principle, one lamp is used. , It is possible to perform an alignment treatment for a long strip-shaped photo-alignment film. Further, an optical element that makes the light from the lamp parallel light is not necessary, and the apparatus can be miniaturized.
JP 2004-163881 A JP 2004-144484 A JP 2002-328234 A Japanese translation of PCT publication No. 2003-508813 JP 2003-156687 A US Pat. No. 6,791,749

When irradiating polarized light to the photo-alignment film, the photo-alignment film may be irradiated through the optical element that transmits or reflects the polarized light emitted from the polarized light irradiation device.
For example, in order to create a processing atmosphere when irradiating polarized light to the photo-alignment film, when a partitioned room is provided, or when a polarized light irradiation device is installed in a factory, the optical path of the polarized light is limited by the height or the floor area occupied For example, it is necessary to wrap around.
In the above, first, the case where a partitioned room is created to create a processing atmosphere will be described.
Because photo-alignment is due to chemical reaction of photo-alignment film (photo-crosslinking, photo-decomposition, photo-dimerization, etc.), depending on the type of alignment film, it is affected by oxygen inhibition such as surface oxidation by light irradiation in the atmosphere. Some reactions may be difficult to proceed or may not complete.
When photo-aligning such a photo-alignment film that is susceptible to oxygen inhibition, if oxygen is reduced from the atmosphere in the vicinity of the photo-alignment film, the effect of oxygen inhibition is reduced, and the light illuminance and energy thresholds required for photo-alignment processing The reaction is likely to proceed, such as lowering.
As a general means for reducing oxygen from the atmosphere in the vicinity of the photo-alignment film, it can be considered that an inert gas such as nitrogen is purged and replaced, or the pressure is reduced.
For example, Patent Document 5 discloses that a photo-alignment film is placed in a sample chamber, gas is introduced to replace air, and polarized light is irradiated.
In the case of the apparatus described in Patent Document 5, a window member (quartz plate) that transmits light is provided in a sample chamber that purges gas, and polarized light that is collimated by a collimator is irradiated through the transmission window.

Next, a case where the optical path of the polarized light is turned back will be described.
For example, in a factory where the polarized light irradiation device is installed, when there is a restriction in the height direction, the polarized light emitted from the polarized light irradiation device 100 is reflected by the reflection mirror 4 to return the light as shown in FIG. The alignment film 31 may be irradiated. For example, FIG. FIG. 5B shows a device configuration for turning back and irradiating polarized light.
However, when the light polarized from the rod-shaped lamp is transmitted through a quartz plate or irradiated through a reflecting mirror as in the apparatus shown in FIG. 7, the polarization axis varies on the light irradiation surface. It was found to occur.
When the optical alignment process is performed with polarized light having a different polarization axis, the contrast of a liquid crystal display element made using the processed optical alignment film varies depending on the location, causing a problem that the liquid crystal display element appears uneven. For this reason, it may be required that the variation of the polarization axis on the light irradiation surface is within ± 0.1 °.

FIG. 8 is a diagram for explaining variations in the polarization axis when polarized light, which is diffused light, passes through a quartz plate. In the figure, the rotation angle of the polarization axis on the light irradiation surface when polarized light is incident on a parallel plate (quartz glass) having a thickness of 1.1 mm at various angles is measured.
FIG. 8A shows the case where the polarization direction (the direction of the polarization axis) is the front-rear direction in the drawing. FIG. 8B shows the case where the polarization direction is the horizontal direction in the drawing.
In either case, when the incident angle of the polarized light on the parallel plate increases, the polarization axis (the direction of the polarized light) rotates, and the variation of the polarization axis in the light irradiation region increases.
FIG. 8C shows a case where the polarization direction is 45 °, which is intermediate between the above (a) and (b). In this case, when the incident angle is increased, the rotation angle of the polarization axis is increased as compared with the above (a) and (b), and the variation of the polarization axis in the light irradiation region is also increased.
In this experiment, the rotation of the polarized light transmitted through the parallel plate was measured. Even when the polarized light was reflected by the reflection mirror, the same rotation of the polarization axis occurred when the incident angle on the reflection mirror was increased.

FIG. 9 shows variations in the polarization axis when polarized light, which is diffused light, is reflected by a reflection mirror.
FIG. 9A shows a case where the polarization direction (direction of the polarization axis) is the front-rear direction in the drawing. FIG. 5B shows the case where the polarization direction is the horizontal direction of the drawing.
FIG. 9C shows the case where the polarization direction is 45 °, which is intermediate between the above (a) and (b). The direction in which the polarization axis deviates (rotates) is opposite to that in the case of transmission, but basically shows the same tendency as in the case of transmission. That is, the larger the incident angle, the more the amount of polarization axis shift (rotation amount). It became bigger.
From the above experiments, it has been found that when polarized light is incident on a transmitting or reflecting optical element with a large incident angle, the polarization axis of the polarized light emitted from the optical element is rotated. In the case of a light source that emits diffused light such as a rod-shaped lamp, polarized light obtained by polarizing the light also becomes diffused light. When the diffused light enters the optical element, the incident light includes a component having a large incident angle, so that the polarization axis rotates, and the polarization axis varies in the light irradiation region.
The present invention has been made to solve the above-described problems, and an object of the present invention is an optical device that transmits or reflects light in an apparatus that irradiates a photo-alignment film with polarized light that is diffused light. Even when the element is arranged in the optical path, it is possible to irradiate the photo-alignment film in the light irradiation region without causing variation in the polarization axis.

If there is an optical element between the polarized light that is the diffused light and the photo-alignment film, the polarization axis varies as described above. Therefore, in the present invention, an optical element is not provided between the wire grid polarizing element and the photo-alignment film. In other words, a wire grid polarizing element is provided between the optical element closest to the photo-alignment film and the photo-alignment film.
For example, as described above, when a partition member is provided to purge the inert gas to replace oxygen or to reduce the pressure, the light transmission window of the sample chamber is an optical element closest to the photo-alignment film. Therefore, the wire grid polarizing element is provided between the light transmission window and the optical alignment film. Further, the light transmission window itself may be a polarizing element.
For example, when a reflection mirror is used to fold the optical path, the reflection mirror is an optical element closest to the photo-alignment film. Therefore, the wire grid polarization element is provided between the reflection mirror and the photo-alignment film.

In the present invention, the following effects can be obtained.
(1) Since no optical element is provided between the polarized light that is the diffused light and the photo-alignment film, variations in the polarization axis do not occur. Therefore, it is possible to irradiate the photo-alignment film with polarized light with little variation in the polarization axis.
(2) By using a wire grid polarizer, diffused light can be polarized efficiently and has a planar shape, so that the space between the light transmission window in the sample chamber and the reflection mirror and the photo-alignment film is wide. Can be prevented.

FIG. 1 shows the configuration of the first embodiment of the present invention.
As in FIG. 5, the light irradiation unit 20 includes a rod-shaped lamp 21 such as a high-pressure mercury lamp or a metal halide lamp, which is a linear light source, and a bowl-shaped condenser mirror 22 that reflects light from the lamp 21. Is built-in.
Hereinafter, a rod-shaped lamp will be described as an example of a linear light source. However, in recent years, LEDs and LDs that emit ultraviolet light have been put into practical use, and such LEDs or LDs are arranged in a straight line and are linear. It is good also as a light source. In that case, the direction in which the LEDs or LDs are arranged corresponds to the longitudinal direction of the lamp.
Currently, as materials for the photo-alignment film, those that are aligned by light having a wavelength of 260 nm ± 20 nm, those that are aligned by light of 280 nm to 330 nm, those that are aligned by light of 365 nm, etc. are known. The type is appropriately selected according to the required wavelength.
Further, in the following description, a case where a linear light source is used will be described. As the light source, a point light source such as an ultrahigh pressure mercury lamp or a xenon mercury lamp, or a surface on which a plurality of the linear light sources or point light sources are arranged on a plane is provided. It can also be applied to a light source having a shape.

As shown in FIG. 1, the work 30 on which the photo-alignment film 31 is formed is placed on a work stage 32, and the entire work stage 32 is housed in the sample chamber 1. The sample chamber 1 is provided with a gas inlet 2a for introducing an inert gas such as nitrogen and a gas outlet 2b for exhausting a gas substituted with the inert gas.
In addition, a light transmission window 3 made of quartz glass is provided in the upper part of the sample chamber 1 so that light from the light irradiation unit 20 is transmitted. The transmitted light is polarized by the wire grid polarizing element 10 provided between the quartz window and the work stage, and is applied to the photo-alignment film 31 on the work stage 32.
Although the polarized light applied to the photo-alignment film 31 is diffused light, there is no optical element that transmits or reflects light between the polarizing element 10 and the photo-alignment film 31, and therefore, as shown in FIGS. 8 and 9. Thus, the rotation of the polarization axis does not occur, and therefore, the polarization axis does not vary.

FIG. 2 is a diagram showing the configuration of the second embodiment of the present invention, in which the light transmission window 3 of the sample chamber 1 is configured by, for example, a wire grid polarizing element.
Other configurations are the same as those shown in FIG. 1. A gas inlet 2 a for introducing an inert gas such as nitrogen into the sample chamber 1 and a gas exhaust for exhausting a gas substituted by the inert gas or the like. An outlet 2b is provided.
Moreover, the light transmission window 3 comprised from a wire grid polarizing element is provided in the upper part of the sample chamber 1, and the light from the light irradiation part 20 is polarized. The polarized light polarized by the light transmission window 3 composed of a polarizing element is applied to the photo-alignment film 31 on the work stage 32.
Also in this case, as in the first embodiment, since there is no optical element that transmits or reflects light between the polarizing element 10 and the photo-alignment film 31, the polarization axis does not rotate, and therefore the polarization axis varies. Does not occur.
In the first and second embodiments, the structure for replacing the inert gas is shown. However, the structure may be such that the sample chamber is evacuated to reduce the pressure.

FIG. 3 is a diagram showing the configuration of the third embodiment of the present invention, and shows a case where the photo-alignment film is formed on a long strip-shaped workpiece.
As shown in the figure, when the photo-alignment film 31 is formed on the long strip-shaped workpiece 30, it is difficult to put the entire strip-shaped workpiece 30 into one sample chamber because the apparatus is large.
However, as shown in the figure, oxygen in the vicinity of the photo-alignment film can be obtained by providing a cover-like sample chamber 1 that covers the portion irradiated with light and allowing an inert gas (nitrogen gas) to flow from the gas inlet 2a. Can be reduced.
As in FIG. 1, a light transmission window 3 (quartz window) that transmits light from the light irradiation unit 20 is provided on the upper portion of the sample chamber 1, and between the light transmission window 3 and the photo-alignment film 31, A wire grid polarizer 10 is provided. The light transmitted through the light transmission window 3 is polarized by the polarizing element 10 and applied to the photo-alignment film 31.
An inert gas such as nitrogen substituted for oxygen is introduced into the sample chamber so as to flow between the polarizing element 10 and the photo-alignment film 31.
Also in this embodiment, since there is no optical element that transmits or reflects polarized light between the polarizing element 10 and the photo-alignment film 31, the rotation of the polarization axis does not occur. The light alignment film is irradiated with no light.

FIG. 4 is a diagram showing the configuration of the fourth exemplary embodiment of the present invention. This embodiment shows a case where the optical path is turned back by a reflecting mirror, and the light alignment film 31 formed on the strip-shaped work 30 is irradiated with polarized light, and this figure is a direction orthogonal to the longitudinal direction of the rod-shaped lamp 22. FIG.
The configuration of the light irradiation unit 20 is basically the same as that in FIG. 1. As described above, diffused light is emitted from the rod-shaped lamp 21, the optical path is turned back by the reflection mirror 4, polarized by the polarizing element 10, and applied to the photo-alignment film 31. Irradiated. The workpiece 30 is, for example, a long continuous workpiece, wound around the delivery roller R1 in a roll shape, drawn out from the delivery roller R1, conveyed, and taken up by the take-up roller R2 under the light irradiation unit 20. It is done.
In this embodiment, the reflection mirror 4 is an optical element closest to the photo-alignment film 31. Therefore, as shown in the figure, the polarizing element 10 is provided between the reflecting mirror 4 and the photo-alignment film 31.
The polarizing element 10 polarizes the light reflected by the reflection mirror 4. Although the polarized light irradiated to the photo-alignment film 31 is diffused light, there is no optical element that transmits or reflects light between the polarization element 10 and the photo-alignment film 31, so that the rotation of the polarization axis is performed as described above. Therefore, the polarization axis does not vary.
In the case where only a desired portion of the photo-alignment film is irradiated with polarized light through a mask or reticle in which a light-shielding portion is formed on the light transmitting member, the mask or reticle is optically closest to the photo-alignment film. It becomes an element. Therefore, the wire grid polarizing element is provided between the mask or reticle and the photo-alignment film.

It is a figure which shows the structure of the 1st Example of this invention. It is a figure which shows the structure of the 2nd Example of this invention. It is a figure which shows the structure of the 3rd Example of this invention. It is a figure which shows the structure of the 4th Example of this invention. It is a figure which shows schematic structure of a wire grid polarizing element. It is a figure which shows the structural example of the polarized light irradiation apparatus which combined the rod-shaped lamp and the wire grid polarizing element. It is a figure which shows schematic structure of the polarized light irradiation apparatus which irradiates an optical path to a light orientation film | membrane using a reflective mirror. It is a figure explaining the dispersion | variation in the polarization axis when the polarized light which is diffused light permeate | transmits a quartz plate. It is a figure which shows the dispersion | variation in the polarization axis when the polarized light which is diffused light is reflected by the reflective mirror.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample chamber 2a Gas inlet 2b Gas exhaust 3 Light transmission window 4 Reflection mirror 10 Wire grid polarizing element
20 Light Irradiation Unit 21 Lamp 22 Condenser Mirror 30 Work 31 Photo Alignment Film 32 Work Stage

Claims (2)

In a polarized light irradiation apparatus that polarizes light and irradiates the photo-alignment film,
Between the light source that emits light and the photo-alignment film, it has one or a plurality of optical elements that transmit or reflect the light from the light source,
A polarized light irradiation apparatus comprising a wire grid polarizing element for polarizing light from a light source between an optical element closest to the photo-alignment film and the photo-alignment film among the optical elements. The optical element closest to the photo-alignment film is
2. The polarized light irradiation apparatus according to claim 1, wherein the polarized light irradiation apparatus is a light transmission member that partitions an atmosphere in the vicinity of the photo-alignment film irradiated with the polarized light from the surrounding atmosphere.

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