JP2001330726A - Polarizing element and method for manufacturing polarizing element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality polarizing element (polarizing plate) which is thin, light in weight and manufactured at a low cost. SOLUTION: The polarizing element 10 comprises an alignment layer 14 formed on a substrate 12 and a hardened liquid crystal layer 16 consisting of a hardenable liquid crystal applied to the alignment layer 14 and hardened in the state aligned with the alignment layer 14. A dichroic pigment is added to the hardeneble liquid crystal and is fixed in an aligned state with the liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel polarizing element (polarizing plate) and a method for manufacturing the same.

[0002]

2. Description of the Related Art A polarizing plate used in a liquid crystal display (LCD) or the like can be formed by uniaxially stretching polyvinyl alcohol (PVA) to which an iodine complex is adsorbed (an iodine-based polarizing plate) or by uniaxially stretching. It is manufactured by a method of adsorbing a dichroic dye on stretched PVA (dye-based polarizing plate).

[0003] The above-mentioned iodine-based polarizing plate is excellent in the degree of polarization and transmittance, and is employed in most high contrast LCDs such as notebook personal computers, LCD monitors, and liquid crystal televisions. On the other hand, the latter dye-based polarizing plate is inferior in iodine type in polarization degree, but has high weather resistance, and is widely used for outdoor applications such as in-vehicle LCDs and polarized sunglasses.

In addition to the above-mentioned conventional polarizing plate or polarizing element, for example, JP-A-7-261024, JP-A-9-197
As described in Japanese Patent Publication No. 125, a polarizing plate or a polarizing element using a combination of a photo-alignment film and a dichroic dye has been proposed.

[0005]

However, an iodine-based polarizing plate and a dye-based polarizing plate are easily torn because PVA is uniaxially stretched. Therefore, two sheets of triacetyl cellulose (TAC) having a size of 50 to 200 μm are used for increasing strength. ) It has a structure sandwiched between protective films such as films, and not only has a very thick structure, but in principle, an expensive non-birefringent film must be used for the protective film, which is expensive. There is a problem that becomes.

[0006] Also, Japanese Patent Application Laid-Open No. Hei 7-261024,
The polarizing plate or the polarizing element described in JP-A-9-197125 cannot be applied unless a dichroic dye which is oriented on a photo-alignment film is used, and even a dye having a high degree of polarization (a large dichroic ratio) can be used. There is a major problem that dichroic dyes that are not aligned on the alignment film cannot be applied.

Further, the polarizing plate or polarizing element described in JP-A-9-197125 is manufactured by repeating a peeling step and a transferring step after aligning a dichroic dye on a photo-alignment film. There is a problem that the low molecular weight dichroic dye which has not been subjected to the process disturbs the orientation during these steps, and the degree of polarization is reduced.

[0008] The present invention has been made in view of the above problems, and is thin without using a reinforcing film.
A high-quality polarizing element that has strength and is capable of applying a dichroic dye, and the degree of polarization does not decrease even when the dichroic dye is applied (hereinafter, the polarizing element includes a polarizing plate in the present invention) And a method for producing the same.

[0009]

Means for Solving the Problems The present inventor has conducted a rubbing treatment on a substrate or forming an alignment film on the substrate, and then applying a curable liquid crystal to which a dichroic dye has been added and aligning the liquid crystal. It has been found that a polarizing element that solves the above problems can be obtained by forming a cured liquid crystal layer by curing with the above method.

According to a first aspect of the present invention, a base material having a rubbed surface and a curable liquid crystal to which a dichroic dye is added are laminated on the rubbed surface of the base material. The above object is achieved by a polarizing element having a cured liquid crystal layer obtained by curing.

[0011] In a second aspect of the present invention, a base material,
An alignment film that is laminated on the base material and controls the alignment of liquid crystal, and a cured liquid crystal layer formed by laminating and curing a curable liquid crystal to which a dichroic dye is added on the alignment film, The above object is achieved by such a polarizing element. .

[0012] The alignment film may be a rubbing alignment film.

The alignment film may be a photo-alignment film.

The photo-alignment film is formed by photoisomerization, photodimerization, photocyclization, photocrosslinking by irradiation of linearly polarized light or obliquely unpolarized light.
Orientation may be performed by any of photolysis and photolysis-bonding.

Further, the curable liquid crystal may be either an ultraviolet curable liquid crystal or an electron beam curable liquid crystal.

According to a first aspect of the present invention, there is provided a method of rubbing a surface of a substrate, and applying a curable liquid crystal to which a dichroic dye is added on the rubbed surface. And a step of irradiating the curable liquid crystal with ultraviolet light or an electron beam to cure the curable liquid crystal, thereby achieving the above object.

In a second aspect of the present invention, a method for applying an alignment film to a surface of a substrate, a step of performing a rubbing treatment on the alignment film, Producing a polarizing element, comprising: a step of applying a curable liquid crystal to which a dichroic dye is added; and a step of irradiating the applied curable liquid crystal with ultraviolet light or an electron beam to cure the liquid crystal. The above object is achieved by a method.

In a third aspect of the present invention, a manufacturing method includes the step of applying a photo-alignment film to the surface of a substrate, and the step of forming a linearly polarized light having a wavelength at which the photo-alignment film exhibits the liquid crystal alignment performance. Or a step of irradiating obliquely non-polarized light, a step of applying a curable liquid crystal to which a dichroic dye is added, on the photo-alignment film aligned by the light irradiation, and applying the applied curable liquid crystal to an ultraviolet ray or an electron. And a step of irradiating with a line to cure the polarizing element.

According to a fourth aspect of the present invention, there is provided a manufacturing method according to the tenth aspect, wherein a step of applying a photo-alignment film to the surface of the base material comprises the step of: Or a step of irradiating oblique non-polarized light at least once through a photomask to perform patterning in a desired alignment direction, and applying a dichroic dye-added curable liquid crystal on the patterned photoalignment film. And a step of irradiating the applied curable liquid crystal with ultraviolet rays or an electron beam to cure the applied liquid crystal, and achieves the above object by a method for manufacturing a polarizing element, comprising: is there.

Further, the photo-alignment film in the method for producing a polarizing element may be any one of photoisomerization, photodimerization, photocyclization, photocrosslinking, photodecomposition and photodecomposition-bonding by irradiation of linearly polarized light or obliquely unpolarized light. Orientation may be performed by such a reaction.

According to the present invention, a curable liquid crystal to which a dichroic dye is added is applied and cured on the rubbed surface of the substrate or on the alignment film on the substrate, thereby eliminating the need for a film for reinforcement. Thus, a high-quality polarizing element that is thin, light, and has no decrease in the degree of polarization can be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, a polarizing element 10 according to an embodiment of the present invention comprises a base material 12 and the base material 1.
2 has an alignment film 14 formed on one surface thereof, and a cured liquid crystal layer 16 to which a dichroic dye is added, formed on the alignment film 14.

The substrate 12 is desirably transparent.
In addition to plate-like inorganic materials such as glass and quartz, various resins such as cellulose acetate, polyester such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyimide, and polyethylene are used.

As shown in FIG. 2A, the alignment film 14 is formed by laminating a film of polyimide, polyamide imide, polyether imide, polyvinyl alcohol or the like on the surface of the base material 12 and, for example, aligning the film by rubbing. It has been processed.

Here, rubbing is a method in which a drum around which a velvet-like cloth made of rayon, cotton, or the like having a short hair is wound, and is brought into contact with the surface of the alignment film 14 while rotating the drum. The alignment film 14 has fine grooves formed in one direction on its surface to align the liquid crystal in contact therewith.

Further, the alignment film 14 may be one subjected to a photo-alignment treatment without using the rubbing method.

This photo-alignment generates anisotropy on the surface of the photo-alignment film by irradiating photoactive molecules such as adbenzene-based polymer and polyvinyl cinnamate with linearly polarized light or obliquely non-polarized light having a wavelength causing a photochemical reaction. In this case, the orientation of the long axis of the molecule on the outermost surface of the film is generated by the incident light, and the driving force for aligning the liquid crystal in contact with the molecule on the outermost surface is formed.

As the material of the photo-alignment film, in addition to the above, photo-isomerization, photo-dimerization, photo-cyclization, and photo-isomerization by irradiation of linearly polarized light or obliquely unpolarized light having a wavelength at which photoactive molecules cause photochemical reactions.
Any of photocrosslinking, photodecomposition, and photodecomposition-bonding may be used as long as it generates anisotropy on the film surface by any of the reactions. For example, "Masaki Hasegawa, Journal of the Liquid Crystal Society of Japan, Vol.3No.1, p3 (1
999) '', `` Yasumasa Takeuchi, Journal of the Liquid Crystal Society of Japan, Vol.3No.4, p262
(1999) "can be used.

When a liquid crystal is applied to the alignment film 14 as described above, the liquid crystal is aligned by using the fine grooves on the surface of the alignment film 14 and / or the alignment of molecules on the outermost surface as a driving force.

It is known that when a dichroic dye is added to the liquid crystal as described above, the dichroic dye in the liquid crystal is oriented along with the orientation of the liquid crystal.

The dichroic dye is a dye having a large difference in absorbance between the major axis direction of the molecule and the direction perpendicular thereto, and when the dichroic dye is anisotropically aligned with the liquid crystal, After passing through the liquid crystal, the ratio of the linearly polarized light component parallel to the molecular long axis direction and the linearly polarized light component perpendicular to the molecular long axis direction is greatly different.

As shown in FIG. 2B, after the curable liquid crystal 16A is coated on the alignment film 14, the cured liquid crystal layer 16 is formed in a specific direction together with the dichroic dye by the alignment film 14. It is cured while being oriented, and the ratio of two linearly polarized light components in the transmitted light is fixed by fixing the orientation of the dichroic dye.

The liquid crystal of the cured liquid crystal layer 16 may be any liquid crystal that can be cured by irradiation of electromagnetic waves, heat or the like. For example, "Harumiyoshi Takatsu, Hiroshi Hasebe, Journal of the Liquid Crystal Society of Japan, Vol.
3 No. 1, p34 (1999) "can be used.

Among these, in particular, they have a C ＝ C double bond such as an acryl group or a methacryl group in the molecule, and are irradiated with ultraviolet rays by irradiation with an electron beam or by adding a photopolymerization initiator (see FIG. 2C). In the case of a liquid crystal which can be subjected to radical polymerization according to ()), the production is easy.

The dichroic dye added to the curable liquid crystal only needs to be compatible with the curable liquid crystal.
Various dichroic dyes described in “Development of 90's functional dyes and market trends, CMC, p10-21” can be used.

The polarizing element 10 according to the embodiment of the present invention
Is a transparent substrate 12 made of, for example, a light-transmitting film.
And the alignment film 14 formed on the base material 12 and the cured liquid crystal layer 16 to which the dichroic dye is added. Therefore, it is not necessary to sandwich the film with an expensive film such as a TAC film, so that it can be formed thin, light and at low cost. Also, since the orientation of the dichroic dye is fixed and the orientation is not disturbed during the manufacturing process, the degree of polarization is high and the quality is high.

When the above-mentioned photo-alignment film is used as the above-mentioned alignment film 14, linearly or obliquely non-polarized light having a wavelength at which a photoactive molecule causes a photochemical reaction is applied to the photo-alignment film. By performing irradiation a plurality of times from different directions through the substrate, complicated patterning becomes possible, whereby a multiaxial polarizing element can be manufactured.

In the above embodiment, the alignment film 14 is obtained by laminating a predetermined film material on the base material 12 and subjecting the base material 12 to an alignment treatment. However, the present invention is not limited to this. Instead, as shown in FIG. 3, the surface of the base material 12 may be directly subjected to an orientation treatment by rubbing to form an orientation treatment surface (rubbing treatment surface) 13.

When a plastic film is used as the base material 12 among the above-mentioned base materials, the molecules on the outermost surface of the base material 12 are oriented in one direction in addition to the fine grooves formed by the rubbing treatment as described above. This also serves as a driving force for aligning the liquid crystal.

[0041]

Embodiments of the present invention will be described below in detail.

Example 1 25 μm thick substrate 12
A rubbing treatment was directly performed on the surface by a conventional method using the above PET film.

UV-curable liquid crystal UCL-001-K1
(Manufactured by Dainippon Ink and Chemicals, Inc.) with black dichroic dye S
After dissolving 2 wt% of -428 (manufactured by Mitsui Toatsu Chemicals) on the surface of the base material using a bar coater, the ultraviolet curable liquid crystal was cured by irradiating non-polarized ultraviolet light. This cured liquid crystal layer has a thickness of 5.0 μm.

The thickness of the obtained polarizing element (polarizing plate) including the substrate 12 is 30.0 μm, which is smaller than the thickness of a general iodine type polarizing element or dye type polarizing plate of 200 to 400 μm. It could be made very thin and light, about 1/10.

When the performance of the obtained polarizing element was measured, the single transmittance and the degree of polarization were 35.2% and 9%, respectively.
4.2, which is almost the same performance as that of a general dye-based polarizing plate.

(Example 2) The thickness of the substrate 12 was 50 μm.
After applying a polyimide-based alignment film SE-5291 (manufactured by Nissan Chemical Industries, Ltd.) with a bar coater using the PEN film of No. 1, the solvent was dried and then baked at 180 ° C. for 60 minutes to form an alignment film. This film thickness was 0.1 μm.

After a rubbing treatment is performed on the alignment film by a conventional method, an ultraviolet-curable liquid crystal UCL-001 is formed thereon.
A solution obtained by dissolving 2% by weight of black dichroic dye S-428 (manufactured by Mitsui Toatsu Chemicals) in -K1 (manufactured by Dainippon Ink and Chemicals, Inc.) was applied by a bar coater onto the rubbed alignment film. Thereafter, the composition was cured by irradiation with non-polarized ultraviolet light. The thickness of the cured liquid crystal layer was 5.2 μm.

Therefore, the thickness of the obtained polarizing element including the substrate 12 is 80.3 μm, which is smaller than the thickness of the above-mentioned general iodine polarizing plate or dye polarizing plate of 200 to 400 μm. It could be made thin and light.

As for the performance of the obtained polarizing element, the single transmittance and the degree of polarization were 34.6% and 96.2, respectively.

(Example 3) 25 μm thick substrate 12
Using a PEN film, a 2 wt% toluene solution of polyvinyl cinnamate was applied to the surface of the substrate 12 with a bar coater, and dried at room temperature to obtain a photo-alignment film having a thickness of 0.1 μm.

Using an ultra-high pressure mercury lamp as a light source, linearly polarized light was extracted through a polarizing filter for ultraviolet light, and the obtained photo-alignment film was irradiated with polarized ultraviolet light.

The photo-alignment film of polyvinyl cinnamate undergoes a dimerization reaction upon irradiation with polarized ultraviolet rays, and is oriented in a direction perpendicular to the polarization axis of the ultraviolet rays.

On this alignment-treated photo-alignment film, a black dichroic dye S-428 (manufactured by Mitsui Toatsu Chemicals Co., Ltd.) was applied to ultraviolet-curable liquid crystal UCL-001-K1 (manufactured by Dainippon Ink and Chemicals, Inc.). ) Was applied by a bar coater and then cured by irradiating unpolarized ultraviolet light. The thickness of this cured liquid crystal layer was 4.8 μm.

The polarizing element thus obtained was used as a substrate 1
The thickness was 30.0 μm even when including No. 2 and was extremely thin and light as compared with the thickness of a general iodine-based polarizing plate or dye-based polarizing plate of 200 to 400 μm.

As to the performance of the obtained polarizing element, the single transmittance and the degree of polarization were 36.6% and 95.1, respectively.

(Example 4) 0.7 m thick as the base material 12
A 2 wt% toluene solution of polyvinyl cinnamate was applied to the surface of this glass plate with a bar coater and dried at room temperature to form a 0.1 μm thick photo-alignment film.

Using an ultrahigh-pressure mercury lamp as a light source, linearly polarized light is extracted through a polarizing filter for ultraviolet light, and a plurality of times of irradiation with polarized ultraviolet light are performed from different directions through a photomask. Then, regions having different orientation directions were formed.

UV-curable liquid crystal UCL-001-K1
(Manufactured by Dainippon Ink and Chemicals, Inc.) with black dichroic dye S
After dissolving 2 wt% of -428 (manufactured by Mitsui Toatsu Chemicals Co., Ltd.), applying the solution on the photo-alignment film by a spin coder, and curing by irradiating non-polarized ultraviolet light. The film thickness of the cured liquid crystal layer thus formed was 5.6 μm.

The obtained polarizing element is a multi-axis polarizing element in which dichroic dyes are oriented in different directions in a plurality of regions different in the irradiation direction of the polarized ultraviolet rays. Was obtained. When the polarizing plate was rotated, the brightness changed every 90 °.

[0060]

As described above, the present invention has an excellent effect that a thin, light, low-cost, high-quality polarizing element can be obtained.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a polarizing element according to a first example of an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a manufacturing process of the polarizing element.

FIG. 3 is an enlarged cross-sectional view showing a polarizing element according to a second example of the embodiment.

[Explanation of symbols]

 10, 20: polarizing element 12: base material 13: alignment treatment surface (rubbing treatment surface) 14: alignment film 16: cured liquid crystal layer 16A: curable liquid crystal

Claims (11)

[Claims] 1. A substrate having a rubbed surface and a cured liquid crystal layer obtained by laminating and curing a curable liquid crystal to which a dichroic dye has been added on the rubbed surface of the substrate. Polarizing element having. 2. A base material, an alignment film laminated on the base material for controlling alignment of liquid crystal, and a curable liquid crystal to which a dichroic dye is added is laminated and cured on the alignment film. And a cured liquid crystal layer. 3. The polarizing element according to claim 2, wherein the alignment film is a rubbing alignment film. 4. A polarizing element according to claim 2, wherein said alignment film is a photo-alignment film. 5. The photo-alignment film according to claim 4, wherein the photo-alignment film is formed of one of photoisomerization, photodimerization, photocyclization, photocrosslinking, photodecomposition, and photodecomposition-bonding by irradiation of linearly polarized light or obliquely unpolarized light. A polarizing element, which is oriented by the reaction of 6. A polarizing element according to claim 1, wherein said curable liquid crystal is one of an ultraviolet curable liquid crystal and an electron beam curable liquid crystal. 7. A step of performing a rubbing treatment on the surface of the base material,
A step of applying a curable liquid crystal to which a dichroic dye is added to the rubbed surface, and a step of irradiating the curable liquid crystal with ultraviolet light or an electron beam to cure the liquid crystal. Device manufacturing method. 8. A step of applying an alignment film on the surface of the base material, a step of rubbing the alignment film, and a step of applying a curable liquid crystal containing a dichroic dye to the rubbed surface. And irradiating the applied curable liquid crystal with ultraviolet light or an electron beam to cure the liquid crystal. 9. A step of applying a photo-alignment film on a surface of a substrate,
A step of irradiating the photo-alignment film with linearly polarized light or obliquely unpolarized light having a wavelength that expresses the alignment performance of the liquid crystal; and, on the photo-alignment film aligned by the light irradiation, a curable liquid crystal to which a dichroic dye is added. A method for producing a polarizing element, comprising: a step of applying; and a step of irradiating the applied curable liquid crystal with ultraviolet light or an electron beam to cure the liquid crystal. 10. A step of applying a photo-alignment film on the surface of a base material, and irradiating the photo-alignment film at least once through a photomask with linearly polarized light or obliquely non-polarized light having a wavelength exhibiting liquid crystal alignment performance. Performing a patterning in a desired alignment direction by applying a curable liquid crystal to which a dichroic dye is added on the patterned photo-alignment film, and aligning the applied curable liquid crystal with an ultraviolet ray. Or a step of irradiating with an electron beam to cure the polarizing element. 11. The photo-alignment film according to claim 9, wherein the photo-alignment film is selected from the group consisting of photo-isomerization, photo-dimerization, photo-cyclization, photo-crosslinking, photo-decomposition and photo-decomposition by linearly polarized light irradiation or obliquely non-polarized light irradiation. A method for producing a polarizing element, wherein the alignment is performed by any of the reactions.