JP4815995B2 - Polarized light irradiation device for photo-alignment - Google Patents

Description

  The present invention relates to a polarized light irradiation apparatus for performing photo-alignment of alignment films such as alignment films of liquid crystal elements and alignment layers of viewing angle compensation films.

In recent years, a technique called photo-alignment has been adopted in which alignment processing is performed by irradiating polarized light of a predetermined wavelength to the alignment film, for alignment processing of alignment films for liquid crystal panels and alignment layers for viewing angle compensation films. It is becoming. Hereinafter, a film provided with an alignment film or alignment layer that performs alignment with light is generally 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 above-mentioned photo-alignment film, for example, the viewing angle compensation film is a strip-like and long work, and is used after being oriented and cut into a desired length. Recently, it has become larger in accordance with the size of the panel, and some have a width of 1500 mm or more.
In order to perform photo-alignment on such a large photo-alignment film, an apparatus using a linear light source (bar-shaped lamp) that matches the width of the alignment film (for example, Patent Document 1, Patent Document 2, and Patent Document 6). ), And an apparatus in which irradiation heads are connected in series according to the width of the alignment film has been proposed (for example, Patent Document 3).

FIG. 7 shows a configuration example of a polarized light irradiation apparatus using a rod-shaped lamp.
A light irradiation unit including a rod-shaped lamp 21 that emits light having a wavelength for performing photo-alignment, such as a high-pressure mercury lamp or a metal halide lamp, and a bowl-shaped condensing mirror 22 that has an elliptical cross section that reflects the light from the lamp 21 20 is arranged so that the longitudinal direction of the lamp 21 is in the width direction of the photo-alignment film 51 formed on the workpiece 50 (perpendicular to the transport direction). The length of the rod-shaped lamp 21 is selected so that the light from the rod-shaped lamp 21 is wider than the width of the photo-alignment film 51 so that the entire width of the photo-alignment film 51 can be irradiated.
The light irradiation unit 20 is provided with a polarizing element unit 10 that is a combination of wire grid polarizing elements. The structure of the polarizing element unit 10 will be described later.
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 51 formed on the workpiece 50 is disposed at the second focal position of the bowl-shaped condenser mirror 22.
The work 50 is, for example, a long continuous work, is wound in a roll shape around the feed roller R1, is pulled out from the feed roller R1, is conveyed, and is taken up by the take-up roller R2 under the light irradiation unit 20. It is done.

When the workpiece 50 is transported under the light irradiation unit, the light alignment 51 of the workpiece 50 is irradiated with light from the rod-shaped lamp 21 polarized by the polarizing element unit 10 and subjected to a light alignment process.
Details of the wire grid polarization element are disclosed in, for example, Patent Document 4 and Patent Document 5.
Wire grid polarizers are formed by arranging a plurality of linear electrical conductors whose length is much longer than their width (for example, metal wires such as chromium and aluminum, hereinafter referred to as grids) on a substrate such as quartz glass in parallel. It is a thing. The pitch P of the electric conductor is not more than the wavelength of the incident light, preferably not more than 1/3.
When the polarizing element is inserted into the electromagnetic wave, most of the polarization (polarization) component parallel to the longitudinal direction of the grid is reflected and the orthogonal polarization (polarization) component passes.
Therefore, in the apparatus shown in FIG. 7 , the light alignment film 51 is irradiated with polarized light along the width direction of the workpiece 50 (longitudinal direction of the lamp 21).
Currently, ultraviolet light having a wavelength of 280 nm to 320 nm is used for photo-alignment. Therefore, the wire grid polarization element used in the polarized light irradiation device for photo-alignment needs a fine processing technique for forming a grid of about 100 nm.
Therefore, using a technique used in semiconductor manufacturing, a grid is formed on a glass substrate (glass wafer) and cut into an appropriate size.

However, the size of a substrate that can be processed by an apparatus used for semiconductor manufacturing is currently up to about φ300 mm, and a large polarizing element that can handle a large-area workpiece cannot be manufactured.
Therefore, when a large polarizing element corresponding to a bar-shaped light source having a long light emission length, for example, a bar-shaped high-pressure mercury lamp or metal halide lamp having a length of 1500 mm, is required, in Patent Document 2, a wire grid polarizing element cut out from a glass substrate is used. It is proposed that a single polarizer is used, and a plurality of polarizers are aligned in the grid direction and aligned along the longitudinal direction of the lamp to be used as a single polarizing element.
However, if the wire grid polarizing elements are simply arranged, the edges of the quartz glass that is the substrate of each wire grid polarizing element have minute chips and irregularities, and direct light from the light source, that is, non-polarized light, from the gaps. Light leaks and the extinction ratio becomes worse. Moreover, the chip | tip of the edge vicinity mentioned above causes the defect | deletion of a grid, and an extinction ratio worsens in the peripheral part of a polarizing element.
To prevent this problem, we providing a light shielding portion on the end portion in the array direction of the polarizing element so as not leak non-polarized light from the abutting portion of the polarizing element, proposed in Japanese Patent Application No. 2004-314056.

Figure 8 is a diagram showing the configuration of the polarization element unit of the first embodiment of the application described above, FIG. 8 (a), view of the polarizing element unit 10 from the optical axis direction of the irradiation light, 8 FIG. 8B is a side view of the polarizing element unit 10, and FIG. 8C is a diagram illustrating an example of attaching a light shielding plate.
As shown in FIGS. 8A and 8B, a plurality of wire grid polarizing elements 1 cut out from the glass substrate are arranged side by side in a frame 2 composed of an upper frame 2a and a lower frame 2b.
A light shielding plate 3 is provided at an end portion (boundary portion) of the polarizing element 1 in the arrangement direction.
Shielding plate 3 is attached, for example, as shown in Figure 8 (c). That is, the frame 2 is composed of an upper frame 2a and a lower frame 2b, a plurality of wire grid polarizing elements 1 are arranged on the lower frame 2b, and an upper frame 2a integrated with a light shielding plate is placed thereon and fixed.
In the figure, the direction of the wire grid formed on the polarizing element is the conveyance direction of the workpiece 50 (the direction orthogonal to the longitudinal direction of the lamp 21). Polarized light in the width direction (the direction along the longitudinal direction of the lamp 21) is irradiated.

When it is desired to irradiate the photo-alignment film 51 with polarized light along the conveyance direction of the workpiece 50 (direction orthogonal to the longitudinal direction of the lamp 21), all the wire grid polarization elements 1 are rotated by 90 ° in FIG. The wire grid may be arranged in the frame 2 so that the direction of the wire grid is the conveyance direction of the workpiece 50 (the direction orthogonal to the longitudinal direction of the lamp 21).
As described above, even when the wire grid polarization element 1 is rotated by 90 ° with respect to FIG. 8 , in the same manner as described above, in the peripheral part of the polarization element, the minute chippings, irregularities, Since there is a problem that the extinction ratio is deteriorated due to the lack of the grid, it is necessary to provide the light shielding plate 3.

As shown in FIG. 8 , by providing the light shielding plate 3, the illuminance of the portion where the light shielding plate 3 is provided decreases, but the non-polarized light does not leak from the gap between the polarizing elements 1 arranged side by side. Will not drop. However, due to the presence of the light shielding plate 3, the illuminance immediately below the light shielding plate 3 is lowered, and the illuminance distribution is deteriorated.
When the illuminance distribution deteriorates, a portion irradiated with polarized light having lower energy than the others may be generated in the alignment film. If the energy of the polarized light irradiated to the alignment film is low, the alignment of the liquid crystal may not be performed sufficiently in the product using the alignment film. This may cause product defects such as lowering.
Without the light shielding plate, the illuminance does not decrease, but non-polarized light is transmitted from the peripheral part or boundary part of the wire grid polarizer, so that the extinction ratio irradiated to the photo-alignment film is deteriorated.
When the extinction ratio is deteriorated, the liquid crystal may not be sufficiently aligned in the product in which the alignment film is used, as in the case where the illuminance is decreased.

On the other hand, in the apparatus in which the irradiation heads shown in Patent Document 3 are arranged in a series, each light irradiation region is not interrupted with respect to the width direction of the photo-alignment film (direction perpendicular to the transport direction). Irradiation is performed so that light irradiation areas from the irradiation head overlap.
However, in such a portion where the light irradiation areas overlap, since the illuminance is the sum of the light from the two irradiation heads, the illuminance can be controlled compared to other areas irradiated by the light from one irradiation head. difficult. Therefore, the illuminance distribution may deteriorate due to the illuminance becoming higher or lower than other regions, and the same problem as described above occurs.
JP 2004-163881 A JP 2004-144484 A JP 2002-350858 A JP 2002-328234 A Japanese translation of PCT publication No. 2003-508813 JP 2004-177904 A

As described above, it is not possible to manufacture a large wire grid polarizing element that can handle a large-area workpiece as described above. If a large-area workpiece is irradiated with light, a plurality of polarizing elements must be used side by side. Absent. Therefore, as described above, the light shielding plate is provided at the boundary portion to prevent the extinction ratio from being lowered. However, there is a problem that the boundary portion is generated between the polarizing elements, the illuminance at the boundary portion is lowered, and the illuminance distribution is deteriorated. Arise.
Similarly, there is a limit to the size that can be produced in the case of a polarizing element with a deposited film or a polarizing element with a glass plate tilted at a Brewster angle, and a single polarizing element can handle large-area workpieces. A large one that can be made cannot be produced.
Therefore, for example, as shown in Patent Document 3, multiple irradiation elements are used in parallel by arranging a plurality of polarizing elements. In this case as well, between the polarized lights by the polarizing elements provided in the respective irradiation heads. There is a boundary portion, and the illuminance of this portion becomes higher or lower than that of other regions, so that the illuminance distribution deteriorates and the irradiation energy distribution deteriorates.
The present invention has been made in view of the above circumstances, and in a polarized light irradiation apparatus that performs light alignment by irradiating polarized light to a large alignment film, the alignment film can be irradiated with polarized light with a uniform energy distribution. It aims at providing the polarized light irradiation apparatus for photo-alignment.

In the present invention, the above problem is solved as follows.
With respect to the photo-alignment film that is continuously or intermittently transported in a straight line, the light irradiation units are arranged in multiple stages along the transport direction of the photo-alignment film.
A linear light source extending in a direction orthogonal to the transport direction of the photo-alignment film and a plurality of wire grid polarizing elements are arranged along the extending direction of the linear light source in each light irradiation section arranged in multiple stages. A polarizing element unit is provided.
In addition, the boundary between the polarizing elements of the light irradiating units at each stage is arranged at each stage so that the boundary between the polarizing elements of the light irradiating units at the other stages and the transport direction of the photo-alignment film do not overlap each other. Each of the light irradiation units thus arranged is arranged with a position shifted in a direction orthogonal to the transport direction of the photo-alignment film.

In the present invention, the light irradiation section is disposed in multiple stages with respect to the conveying direction of the photo-alignment film, the boundary portion of the wire grid Henkomoto terminal of the light irradiation section disposed in each stage, the light irradiation portion of the other stages of so as not to overlap each other with respect to the conveying direction of the boundary portion and the photo-alignment film of Henkomoto child was staggered position in a direction perpendicular to the conveying direction of the optical alignment layer with light irradiation unit arranged in each stage Therefore, the entire alignment film can be irradiated with polarized light with a uniform energy distribution.
That is, the illuminance on the photo-alignment film corresponding to the boundary part of the polarizing element is low (or high), but the boundary part of the polarizing element of each stage of the light irradiation unit is in a direction orthogonal to the transport direction of the photo-alignment film. The illuminance distribution on the photo-alignment film is integrated by sequentially irradiating light on the photo-alignment film from the multi-stage light irradiation unit, and as a result, the entire photo-alignment film has a uniform UV energy. Polarized light is irradiated with the distribution.
Therefore, it is possible to prevent the occurrence of a portion where the energy of the irradiated polarized light is insufficient in the photo-alignment film.

It shows the configuration of a polarized light irradiation apparatus of the embodiment of the present invention in FIG.
The light irradiators 20A and 20B include 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 condensing mirror 22 having an elliptical cross section for reflecting light from the lamp 21. Built in.
The light irradiation units 20 </ b> A and 20 </ b> B are arranged so that the longitudinal direction of the lamp 21 is in the width direction of the photo-alignment film 51 formed on the workpiece 50 (perpendicular to the transport direction).
The rod-shaped lamp 21 has a longitudinal direction that coincides with the longitudinal direction of the bowl-shaped condenser mirror 22, and a substantially central portion of the cross section coincides with the first focal position of the elliptical bowl-shaped condenser mirror 22. The photo-alignment film 51 formed on the workpiece 50 is disposed at the second focal position of the bowl-shaped condenser mirror 22.
The work 50 is, for example, a long continuous work, is wound in a roll shape around a feed roller (not shown), is pulled out from the feed roller and conveyed, and passes under the light irradiation units 20A and 20B. It is wound on a take-up roller.
Wire grid polarization element units 10 and 10 'shown in FIG. 8 are provided on the light emitting side of the light irradiation units 20A and 20B. As described above, the wire grid polarizing element units 10 and 10 ′ are provided with the light shielding plate 3 at the end portion (boundary portion) of the polarizing element 1 in the arrangement direction.

In the following, 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. A linear light source may be used. In that case, the direction in which the LEDs or LDs are arranged corresponds to the longitudinal direction of the lamp.
Further, as materials for photo-alignment films, there are known materials that are aligned with light having a wavelength of 260 nm ± 20 nm, materials that are aligned with light of 280 nm to 330 nm, and materials that are aligned with light of 365 nm. The type is appropriately selected according to the required wavelength.

Blocks 23 are attached to both sides of the light irradiation units 20 </ b> A and 20 </ b> B in the longitudinal direction of the lamp 21, and support columns 24 are attached via the blocks 23. The work 50 on which the photo-alignment film 51 is formed is conveyed between the two struts 24.
A plurality of light irradiation units 20 </ b> A and 20 </ b> B that emit such polarized light are provided in multiple stages along the conveyance direction of the workpiece 50. FIG. 1 shows a case in which the light irradiators 20A and 20B are arranged in two stages. The following description will be made by taking the case of two stages as an example, but three or more stages may be provided.
Here, each light irradiation part 20A, 20B arranged in each stage is different from the boundary part (part where the light shielding plate 3 is provided) between the polarizing elements 1 of the light irradiation parts 20A, 20B in each stage. In order to avoid overlapping with the boundary part of the polarizing element 1 of the light irradiation part of the stage and the transport direction of the photo-alignment film 51, the positions are shifted in the direction orthogonal to the transport direction.
That is, as shown in FIG. 2, the light-shielding plates 3 of the wire grid polarization element units 10 and 10 ′ of the light irradiation units 20A and 20B provided in two stages do not overlap with the workpiece conveyance direction (in a straight line shape). So as not to line up). Similarly, when three or more light irradiation units are provided, the light shielding plate 3 is arranged so as not to overlap with the workpiece conveyance direction (so as not to be aligned in a straight line).
1 shows a case where five and six wire grid polarizing elements are provided in the light irradiators 20A and 20B, respectively, FIG. 2 shows a wire grid polarizing element unit composed of eight wire grid polarizing elements. The case where is used is shown.

Next, the operation of the apparatus shown in FIG. 1 will be described.
When the work 50 is transported, the photo-alignment film 51 is first irradiated with polarized light from the light irradiation unit 20B, and then irradiated with polarized light from the light irradiation unit 20A.
The light shielding plate 3 is provided at the boundary between the plurality of wire grid polarizers 1 arranged in the polarizing element unit 10 ′ of the light irradiation unit 20 B. Therefore, the photo-alignment film 51 transported directly below the light shielding plate 3. This part is irradiated with polarized light with low illuminance as shown in FIG.
The light shielding plate 3 is also provided at the boundary between the plurality of wire grid polarizers 1 arranged in the polarizing element unit 10 of the light irradiation unit 20A. Therefore, the photo-alignment film 51 transported directly below the light shielding plate 3 is provided. The portion is irradiated with polarized light with low illuminance as shown in FIG.
However, since the positions of the light shielding plates 3 of the polarizing element units 10 ′ and 10 are arranged so as not to overlap with each other (so as not to be aligned in a straight line) with respect to the workpiece conveyance direction, the light irradiation unit 20B The portion irradiated with low illuminance in the polarized light irradiation is irradiated with high illuminance in the polarized light irradiation by the next light irradiation unit 20A, and the portion irradiated with low illuminance in the polarized light irradiation by the light irradiation unit 20A is First, irradiation with polarized light by the light irradiation unit 20B is performed with high illuminance.
Therefore, the photo-alignment film 51 irradiated with polarized light passing under both of the light irradiation units 20A and 20B is integrated with the illuminance distribution of both as shown in FIG. 2C, resulting in uniform energy. Polarized light is irradiated with the distribution. As a result, in the photo-alignment film 51, it is possible to prevent a portion where the energy of the irradiated polarized light is insufficient.

The workpiece 50 may be a long strip-shaped workpiece wound around a roll, or may be a rectangular workpiece shaped to the size of, for example, a liquid crystal panel on which the photo-alignment film 51 is formed. .
When the work 50 is rectangular, the work 50 is placed on a work stage (not shown), and the work stage is linearly moved while irradiating polarized light from the light irradiation units 20A and 20B, so that the photo-alignment processing of the photo-alignment film is performed. To do.
In addition, when irradiating polarized light to the photo-alignment film 51 of the work 50 and performing photo-alignment processing, the work 50 may be continuously moved while irradiating the polarized light, or while moving the work intermittently. You may irradiate with polarized light.
When the workpiece 50 is moved intermittently, for example, after the workpiece 50 is moved by a certain amount, the workpiece 50 is stopped and irradiated with polarized light, and then the irradiation of polarized light is stopped and the workpiece is moved by a certain amount. Then, the operation of stopping the workpiece and irradiating the polarized light is repeated.
Further, not only in one direction but also the workpiece 50 may be reciprocated to irradiate polarized light, for example, as in the light irradiation unit 20B → 20A → 20A → 20B.
Furthermore, instead of moving the work stage, the light irradiation units 20A and 20B may be moved on the work 50 to perform the photo-alignment process of the work 50.

Next, an experimental result of examining the effect of uniform energy distribution using a light irradiation apparatus in which the position of the light shielding plate 3 of the polarizing element unit is shifted so as not to overlap the workpiece conveyance direction is shown.
FIG. 3 is a diagram illustrating how the wire grid polarization element units are arranged in the light irradiation unit arranged in multiple stages in the workpiece conveyance direction.
As shown in FIG. 3, there are four light irradiation units, that is, the light irradiation units 1 to 4, which are arranged along the workpiece conveyance direction. As shown in the figure, the light shielding plate 3 of the wire grid polarizing element unit of each light irradiation unit is arranged so as not to overlap with the workpiece conveyance direction (so as not to be aligned in a straight line). .
In such an arrangement of the wire grid polarization element unit, the light irradiation part (wire grid polarization element unit) has only one stage, the light irradiation part (wire grid polarization element unit) has two stages, and the light irradiation part (wire grid polarization element unit). ) Was measured for UV energy (average illuminance) distribution in each case with four stages. Here, the average illuminance means the average illuminance when the workpiece is moved in the transport direction.

The results are shown in FIGS. FIG. 4 shows a case where only the light irradiation unit 1 of FIG. 3 is used as the light irradiation unit.
The vertical axis represents the UV energy (unit mJ / cm ² ) irradiated to the photo-alignment film, the horizontal axis represents the distance in the width direction (unit mm) from the center of the workpiece, and the same applies to FIGS.
As shown in FIG. 4, in the light irradiation unit 1 alone, an illuminance distribution is generated by the light shielding unit, and the energy distribution in the light irradiation region is calculated by the following formula, and is ± 8.5%.
Energy distribution (±%) = {(maximum energy value−minimum energy value) / (maximum energy value + minimum energy value)} × 100
FIG. 5 shows a case where two stages of the light irradiation unit 1 and the light irradiation unit 2 of FIG. 3 are used as the light irradiation unit. The lower graph in the figure shows the energy distribution in each of the light irradiation unit 1 and the light irradiation unit 2, and the energy distribution is about ± 8% to 10% from the above formula. Then, the irradiated UV energy is doubled, and the low illuminance part of one light irradiation part is canceled out by the high illuminance part of the other light irradiation part, as in the graph shown above The energy distribution was improved to ± 2.8%.
FIG. 6 shows a case where all four stages from the light irradiation unit 1 to the light irradiation unit 4 in FIG. 3 are used as the light irradiation unit. The lower graph in the figure shows the energy distribution of each of the light irradiation unit 1 to the light irradiation unit 4, and the energy distribution is about ± 8% to 10% from the above formula. Then, the irradiated UV energy is quadrupled and the unevenness of the illuminance distribution of each light irradiation part is offset, and the energy distribution is improved to ± 1.5% as shown in the graph above. It was.

It is a figure which shows the structure of the polarized light irradiation apparatus of the Example of this invention. It is a figure which shows arrangement | positioning and energy distribution of a polarizing element unit. It is a figure which shows how to arrange the wire grid polarizing element unit of the light irradiation part arrange | positioned along with the conveyance direction of a workpiece | work in multiple stages. It is a figure which shows energy distribution in case a light irradiation part is one step. It is a figure which shows energy distribution in case a light irradiation part is two steps | paragraphs. It is a figure which shows energy distribution in case a light irradiation part is four steps | paragraphs. It is a figure which shows the structural example of the polarized light irradiation apparatus using a rod-shaped lamp. It is a figure which shows the structure of a polarizing element unit.

DESCRIPTION OF SYMBOLS 1 Wire grid polarizing element 3 Light-shielding plate 10,10 'Polarizing element unit 11 Polarizing element 20A, 20B Light irradiation part 21 Bar-shaped lamp 22 Gutter-shaped condensing mirror 23 Block 24 Prop 50 Work 51 Photo-alignment film

Claims (1)

With respect to the photo-alignment film that is continuously or intermittently linearly transported, the light irradiation sections are arranged in multiple stages along the direction of transport of the photo-alignment film, and from the light irradiation sections arranged in multiple stages to the photo-alignment film A polarized light irradiation apparatus for irradiating polarized light to perform photo-alignment,
Each light irradiation part arranged in the above-mentioned multi-stage,
A linear light source extending in a direction perpendicular to the transport direction of the photo-alignment film;
A plurality of wire grid polarizing elements are arranged along the direction in which the linear light source extends, and the polarizing element unit has a boundary portion between the arranged wire grid polarizing elements,
Each light irradiation unit arranged in each stage is such that the boundary between the polarizing elements of the light irradiation units of each stage is in the transport direction of the polarizing element of the light irradiation unit of the other stage and the photo-alignment film On the other hand, the polarized light irradiation device for photo-alignment is characterized in that the position is shifted in a direction orthogonal to the transport direction of the photo-alignment film so as not to overlap each other.

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