JP2007241037A - Polarizing element, manufacturing method thereof, and liquid crystal display element - Google Patents

Abstract

Provided is a polarizing element having a retardation control layer that can be easily and inexpensively manufactured with little variation in the optical axis of the refractive index and the orientation angle with a substrate in a predetermined axial direction such as the width direction.
A polarizing element 1 having at least one phase difference control layer 3 and a polarizing film 2, wherein the phase difference control layer 3 has an strict angle ± 1 ° with respect to a substrate. A lyotropic liquid crystal compound that is vertically or horizontally oriented with a refractive index whose fast axis is less than ± 1 ° with respect to the polarization transmission axis and is perpendicular or parallel to the in-plane direction or parallel to the thickness direction. A polarizing element.
[Selection] Figure 1

Description

The present invention relates to a polarizing element having a retardation control layer that can be easily manufactured with little variation in refractive index in a predetermined axial direction such as the width direction, a manufacturing method thereof, and a liquid crystal display element.
The term “lyotropic liquid crystalline compound” refers to a compound having liquid crystal performance in a specific temperature range when dissolved in a specific concentration range in water or an organic solvent. It does not indicate a state having liquid crystallinity. The “orientation angle with respect to the polarizing film (base material)” is more preferably less than ± 0.5 °. Further, the variation in the refractive index in the predetermined axial direction is more preferably less than ± 0.5 °.

Liquid crystal display devices are widely used as display devices for personal computers and the like because they can be thinned with low voltage and low power consumption. In recent years, it is also used for large TVs. However, as the liquid crystal screen becomes larger, there is an increasing demand for a wider viewing angle, and a phase difference control layer has been used to expand the viewing angle. For this reason, the phase difference control layer tends to be further widened as the liquid crystal screen is enlarged.
In general, such a retardation control layer is produced by controlling the alignment of liquid crystal molecules by stretching a film or aligning a film, rubbing treatment or the like.

  However, the retardation control layer that is controlled in orientation by stretching the film tends to cause a phenomenon in which the orientation axis varies depending on the width direction, and it is difficult to produce a retardation control layer having a uniform orientation axis in the width direction. there were. It is known that such misalignment of the alignment axis causes a significant decrease in display contrast.

  As a means for solving such a problem, Patent Document 1 discloses that a reduction in contrast is reduced by adjusting a shift of an axis when a retardation control layer is bonded to a polarizing plate. However, in this method, there is a problem that the variation of the in-plane alignment axis is not mentioned and the effect is not sufficient.

  Patent Document 2 discloses a method of softening the film by adjusting the temperature during stretching to eliminate stretching unevenness. However, the range of variation in the orientation axis is within 3 °, and in this range, a large-sized liquid crystal display element is used. It is very difficult to use as.

  In this way, in the process of stretching in a direction other than the film transport direction, in consideration of the fact that it is very difficult to suppress the variation of the orientation axis to 0 °, in Patent Document 3, the left and right gripping means are controlled independently. A manufacturing method is disclosed in which in-plane alignment axis unevenness is periodically varied within a certain range to substantially prevent a decrease in contrast. However, there are problems that the manufacturing method such as the adjustment of the left / right temperature balance and the air volume balance is complicated, and the film is easily broken during the manufacturing.

  In addition, the retardation control layer prepared by controlling the alignment of liquid crystal molecules has a feature that a uniform alignment axis can be obtained. However, an alignment film and / or a rubbing treatment is required for its manufacture. There was a problem that the process was complicated and not easy (Patent Documents 4 to 6).

In addition, a retardation control layer is also known which is prepared by using an lyotropic liquid crystalline compound and performing alignment control by shearing without using an alignment film and a rubbing treatment (Patent Documents 7 and 8). In any of the patent documents, attention is paid to the orientation in the surface of the retardation control layer due to shearing of the lyotropic liquid crystal compound, but the orientation angle with respect to the substrate is not taken into consideration. For this reason, when used as a phase difference control layer for the purpose of wide viewing angle, there is a problem that unevenness of display contrast tends to occur.
JP-A-11-160536 JP 2001-215332 A JP 2005-331915 A JP-A-8-50206 JP 2001-154019 A JP 2004-317651 A JP 2002-296415 A JP 2002-277633 A

The present invention provides a polarizing element and a liquid crystal display element having a retardation control layer that can be easily manufactured with little variation in the optical axis of the refractive index in a predetermined axial direction and without requiring an alignment film or a rubbing treatment. For the purpose.
In particular, it is an object of the present invention to provide a polarizing element having a retardation control layer that can be easily formed without requiring an alignment film or a rubbing process in the VA mode or IPS mode with little variation in the optical axis.

  The invention of claim 1 is a polarizing element having at least one retardation control layer and a polarizing film, wherein the retardation control layer contains a lyotropic liquid crystalline compound, and the lyotropic liquid crystalline compound is a polarizing film. The orientation angle is less than ± 1 ° and the orientation is vertical or horizontal, and the fast axis of the refractive index of the retardation control layer is less than ± 1 ° with respect to the polarization transmission axis. The polarizing element is characterized by being perpendicular to or parallel to the thickness direction.

  The invention of claim 2 is a method for producing a polarizing element having at least one phase difference control layer and a polarizing film, wherein a coating liquid containing a lyotropic liquid crystalline compound is applied to the polarizing film while shearing. Forming a retardation control layer by fixing the orientation of the lyotropic liquid crystalline compound by drying the coating liquid, wherein the lyotropic liquid crystalline compound is perpendicular to the polarizing film at an orientation angle of less than ± 1 °. It is oriented or horizontally oriented, and the fast axis of the refractive index of the phase difference control layer is formed perpendicular to the in-plane direction or parallel to the thickness direction at an angle less than ± 1 ° with respect to the polarization transmission axis. This is a method for manufacturing a polarizing element.

  The invention of claim 3 is a method for producing a polarizing element having at least one phase difference control layer and a polarizing film, wherein a coating liquid containing a lyotropic liquid crystalline compound is applied to a transparent substrate while applying shear. A step of drying the coating liquid to align and fix the lyotropic liquid crystalline compound to form a retardation control layer, and a step of bonding the transparent substrate on which the retardation control layer is formed and the polarizing film, The lyotropic liquid crystalline compound is oriented vertically or horizontally with an orientation angle with respect to the substrate of less than ± 1 °, and the fast axis of the refractive index of the retardation control layer is an angle with respect to the polarization transmission axis. It is a manufacturing method of a polarizing element, characterized in that the polarizing element is formed to be less than ± 1 ° or perpendicular to the in-plane direction or parallel to the thickness direction.

  The invention of claim 4 is a method for producing a polarizing element having at least one retardation control layer and a polarizing layer, and a coating liquid containing a lyotropic liquid crystalline compound is applied to a transparent substrate while shearing. A step of drying and fixing the lyotropic liquid crystalline compound to form a phase difference control layer by drying the coating liquid, and a surface of the transparent substrate on which the phase difference control layer is formed is polarized on the tooth retraction surface. Forming a layer, wherein the lyotropic liquid crystalline compound is vertically or horizontally oriented with an orientation angle of less than ± 1 ° with respect to the substrate, and the fast axis of the refractive index of the retardation control layer Is a method of manufacturing a polarizing element, characterized in that it is formed perpendicular to the in-plane direction or parallel to the thickness direction at an angle of less than ± 1 ° with respect to the polarization transmission axis.

  The invention according to claim 5 includes a step of polymerizing and fixing by irradiating heat or ultraviolet rays in a state where the lyotropic liquid crystalline compound exhibits polymerizability and the lyotropic liquid crystalline compound is aligned. 4. A method for producing a polarizing element according to any one of 4 above.

  The invention of claim 6 includes a step of polymerizing and immobilizing the coating liquid containing the lyotropic liquid crystalline compound by heat or ultraviolet irradiation in a state where the lyotropic liquid crystalline compound further contains a polymerizable compound and the lyotropic liquid crystalline compound is aligned. It is a manufacturing method of the polarizing element in any one of Claims 2-5.

  A seventh aspect of the present invention is a liquid crystal display element including at least one liquid crystal cell and the polarizing element according to the first aspect.

  The invention of claim 8 is characterized in that the liquid crystal cell is a liquid crystal cell of a vertical alignment mode in which the liquid crystal is aligned substantially vertically when no voltage is applied and is aligned substantially horizontally when a voltage is applied. Item 8. The liquid crystal display element according to Item 7.

  According to a ninth aspect of the invention, the liquid crystal cell has an electrode on at least one of the liquid crystal cells, the liquid crystal is aligned parallel to the substrate between a pair of transparent substrates, and the liquid crystal cell 8. The liquid crystal display according to claim 7, wherein the direction of the molecular major axis is a liquid crystal cell configured to change in a plane parallel to the substrate by a change in voltage applied to the liquid crystal cell. It is an element.

The present invention provides phase difference control with little variation in refractive index in a predetermined axial direction because it exhibits birefringence by a lyotropic liquid crystal compound formed by alignment by shear coating of a lyotropic liquid crystal and interaction with a polarizing film (base material). There exists an effect that the polarizing element which has a layer can be produced.
In addition, a retardation control layer is formed directly on the polarizing film, a retardation control layer is formed on the protective base material on which the polarizing film is formed, and then a polarizing element is bonded to the polarizing layer, or a transparent base material is provided. By forming a phase difference control layer and then bonding it to a polarizing element, an alignment film and a rubbing treatment that are necessary for a phase difference control layer using a conventional liquid crystal compound are unnecessary, and a polarizing element having a phase difference control layer is provided. There is an effect that it can be manufactured easily and inexpensively.
Further, the fast axis of the refractive index of the phase difference control layer is less than ± 1 ° with respect to the polarization transmission axis and is perpendicular or parallel to the in-plane direction or parallel to the thickness direction. There exists an effect that it can apply to a display element.

  The present invention is a polarizing element having at least one retardation control layer and a polarizing film, wherein the lyotropic liquid crystalline compound is vertically or horizontally aligned with an orientation angle of less than ± 1 ° with respect to the polarizing film. The polarizing element is characterized in that the phase advance axis of the refractive index of the phase difference control layer is less than ± 1 ° with respect to the polarization transmission axis and is perpendicular or parallel to the in-plane direction or parallel to the thickness direction. And a manufacturing method thereof and a liquid crystal display device including the polarizing element.

  By reducing the optical axis variation angle of the refractive index in a predetermined axial direction to less than ± 1 °, more preferably less than ± 0.5 °, it is possible to prevent the display contrast from being lowered. Control of the variation in the optical axis of the refractive index in the predetermined axial direction can be performed by controlling the alignment in the retardation film plane and the variation in the orientation angle with respect to the polarizing film.

  In addition, since the fast axis of the refractive index of the phase difference control layer is perpendicular or parallel to the in-plane direction or parallel to the thickness direction with respect to the polarization transmission axis, the display liquid crystal driving cell is a VA mode or IPS mode liquid crystal. A drive cell is preferred.

  1 and 2 show an embodiment of the liquid crystal display element of the present invention. 1 and 2 includes a polarizing element having a polarizing film and a phase difference control layer, a display driving liquid crystal cell, and a polarizing element.

  The retardation control layer of the present invention is characterized by containing a lyotropic liquid crystalline compound. Specifically, while applying a shearing coating liquid in a lyotropic liquid crystal state, a polarizing film, and a protective substrate for the polarizing layer in a subsequent step, It is applied to a transparent base material or another base material, and after aligning the lyotropic liquid crystalline compound by utilizing the interaction with the polarizing film (base material), the orientation is fixed to form a retardation control layer It is. At this time, an alignment film and a rubbing treatment that are necessary in a phase difference control layer using a conventional liquid crystal compound are not required. Moreover, unlike the retardation control layer produced by extending | stretching a film, a refractive index can be arrange | equalized in a predetermined axial direction.

The polarizing film in this invention is not specifically limited, A well-known polarizing film can be used. For example, a polarizing film in which a polarizing layer made of a stretched polyvinyl alcohol film and an iodine complex is sandwiched between two protective substrates, a polarizing layer made of a stretched film of polyvinyl alcohol and a dichroic dye is two protective substrates Examples thereof include a polarizing film sandwiched between 2 and a polarizing film formed by sandwiching a polarizing layer made of an oriented dichroic dye between two protective substrates.
Although the said protective base material is not specifically limited, A cellulose acetate film, a glass substrate, etc. can be illustrated. In addition, those obtained by subjecting these substrates to a surface treatment such as a hydrophilic treatment or a hydrophobic treatment can also be used.

  In addition, when the retardation control layer is provided on a transparent substrate different from the protective substrate of the polarizing film, and the retardation control layer and the polarizing film are bonded later, the transparent substrate is not particularly limited. A cellulose acetate film, a glass substrate, etc. can be illustrated although there is no.

In addition, when a retardation control layer is provided on one surface of a protective substrate constituting a polarizing film and a polarizing layer is formed on the opposite surface, the forming method is not limited, and various methods are used. Can do.
For example, a method of bonding a stretched film of polyvinyl alcohol and a polarizing layer made of an iodine complex, a method of applying and forming a polarizing material, and the like can be mentioned.

In order to perform vertical alignment or horizontal alignment at an angle of orientation of less than ± 1 ° with respect to the polarizing film, the interaction with the substrate is important, and the means is not particularly limited. Examples of effective means include molecular design according to the material and surface treatment of the substrate.
In addition, the orientation angle with respect to a polarizing film here is an orientation angle with respect to the base material which comprises a polarizing film. Moreover, when providing a phase difference control layer on another base material and sticking with a polarizing film later, it is an orientation angle with respect to the base material used for a phase difference control layer.

  The means for utilizing the interaction with the polarizing film is not particularly limited. Examples of effective means include molecular design tailored to the substrate constituting the polarizing film and surface treatment of the substrate. In particular, since the protective substrate of the polarizing element used in the liquid crystal display element is mainly a triacetyl cellulose (TAC) film that has been hydrophilized by a saponification treatment, the interaction with a saponified TAC film is considered This molecular design has the advantage that the orientation angle relative to the substrate can be controlled without increasing the cost and the number of steps.

  In addition to the lyotropic liquid crystalline compound, water, or an organic solvent, a polymerizable compound, a surfactant, and the like can be added to the coating solution as long as the shear orientation of the lyotropic liquid crystalline compound is not lowered. As the organic solvent, acetone, 2-propanol, dioxane, methanol, ethanol, ionic liquid, or the like can be used.

  As the lyotropic liquid crystalline compound, those exhibiting lyotropic liquid crystallinity whose alignment can be easily controlled by shear flow are preferable. As such compounds, chromonic dyes, compounds described in non-patent literature (M. Yoshio et al., J. Am. Chem. Soc., 2004, 126, 994-995.) And the like are known. Examples of chromonic dyes include cromoglycate sodium salt (DSCG: compound represented by chemical formula (1)), acenaphthoquinoxaline sulfonate, and the like. Moreover, what has superposition | polymerization performance can also be used for the said lyotropic liquid crystal compound.

  As a coating method for the coating solution, wet coating methods such as slot die coating and wire bar coating can be used.

  Examples of the alignment fixing method include a method in which the solvent of the coating solution is evaporated or polymerization is performed by heat or ultraviolet irradiation in a state where the lyotropic liquid crystalline compound obtained by shear coating is aligned.

In the present invention, a protective layer for protecting the retardation control layer may be provided.
The protective layer is preferably a layer having chemical resistance, high transmittance, and optically isotropic properties. Examples of such a protective layer include a silica film.

<Example 1>
A triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was used as a transparent substrate, and hydrophilic treatment was performed by saponification treatment.
A lyotropic liquid crystalline ink (VAE003 manufactured by Optiva Inc) was applied to the substrate using a # 2 wire bar.
After coating, drying was performed at room temperature to obtain a coated film. Arbitrary 20 points of the obtained coating film were measured for the orientation direction of the in-plane fast axis with respect to the coating direction and the orientation angle with respect to the substrate using Mueller Matrix Polarimeters manufactured by Axometrics. It was found that there was little variation in the orientation angle with respect to the axis of the refractive index and the substrate at 3 ° and 0 ° ± 0.4 °.
Separately, a saponified triacetylcellulose film (manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was coated with Optiva's N015 ink to produce a polarizing film, and then bonded to the triacetylcellulose film with the retardation control layer and polarized. An element was obtained.

<Example 2>
NPF-SEG1224DU manufactured by Nitto Denko was used as the polarizing film, and hydrophilic treatment was performed by plasma treatment. Next, lyotropic liquid crystalline ink (VAE003 manufactured by Optiva Inc) was applied to the polarizing plate using a # 2 wire bar.
After coating, drying was performed at room temperature to obtain a coated film. Next, 500 nm was provided as a protective layer on the coating film by SiOx and sputtering. The obtained polarizing element is immersed in distilled water for 10 hours, the film on the coating film side is peeled off from the polarizing element and dried. Then, in the same manner as in Example 1, the orientation direction of the in-plane phase axis of the coating film and the substrate When the orientation angle was measured, it was found to be 0 ° ± 0.4 ° and 0 ° ± 0.4 °, a phase difference control layer with little variation in orientation angle with respect to the refractive index axis and the substrate. . From the above, it was found that a polarizing element provided with a retardation control layer can be produced.

It is a schematic block diagram which shows an example of the liquid crystal element of this invention. It is a schematic block diagram which shows an example of the liquid crystal element of this invention.

Explanation of symbols

1 polarizing element,
2 Polarizing film 3 Phase difference control layer 4 Display driving liquid crystal cell 5 Transparent substrate

Claims (9)

A polarizing element having at least one retardation control layer and a polarizing film,
The retardation control layer contains a lyotropic liquid crystalline compound;
The lyotropic liquid crystalline compound is oriented vertically or horizontally with an orientation angle with respect to the polarizing film of less than ± 1 °,
The polarizing element is characterized in that the fast axis of the refractive index of the phase difference control layer is less than ± 1 ° with respect to the polarization transmission axis and is perpendicular or parallel to the in-plane direction or parallel to the thickness direction. A method of manufacturing a polarizing element having at least one retardation control layer and a polarizing film,
A step of applying a coating liquid containing a lyotropic liquid crystalline compound to the polarizing film while shearing, a step of forming a retardation control layer by fixing the orientation of the lyotropic liquid crystalline compound by drying the coating liquid,
The lyotropic liquid crystalline compound is oriented vertically or horizontally with an orientation angle with respect to the polarizing film of less than ± 1 °, and the fast axis of the refractive index of the retardation control layer is relative to the polarization transmission axis A method of manufacturing a polarizing element, characterized in that the polarizing element is formed at an angle of less than ± 1 ° and perpendicular or parallel to the in-plane direction or parallel to the thickness direction. A method of manufacturing a polarizing element having at least one retardation control layer and a polarizing film,
A step of applying a coating liquid containing a lyotropic liquid crystalline compound to a transparent substrate while applying shear, a step of forming a retardation control layer by fixing the orientation of the lyotropic liquid crystalline compound by drying the coating liquid, and a phase difference control A step of laminating a transparent substrate on which a layer is formed and a polarizing film;
The lyotropic liquid crystalline compound is oriented vertically or horizontally with an orientation angle with respect to the substrate of less than ± 1 °, and the fast axis of the refractive index of the retardation control layer is relative to the polarization transmission axis A method of manufacturing a polarizing element, characterized in that the polarizing element is formed at an angle of less than ± 1 ° and perpendicular or parallel to the in-plane direction or parallel to the thickness direction. A method of manufacturing a polarizing element having at least one retardation control layer and a polarizing layer,
A step of applying a coating liquid containing a lyotropic liquid crystalline compound on a transparent substrate while applying shear, a step of forming a retardation control layer by fixing the orientation of the lyotropic liquid crystalline compound by drying the coating liquid, the transparency A step of forming a polarizing layer on the surface where the phase difference control layer of the substrate is formed and the surface of the tooth retraction;
The lyotropic liquid crystalline compound is oriented vertically or horizontally with an orientation angle with respect to the substrate of less than ± 1 °, and the fast axis of the refractive index of the retardation control layer is relative to the polarization transmission axis A method of manufacturing a polarizing element, characterized in that the polarizing element is formed at an angle of less than ± 1 ° and perpendicular or parallel to the in-plane direction or parallel to the thickness direction.   The lyotropic liquid crystalline compound exhibits polymerizability, and includes a step of polymerizing and fixing by heat or ultraviolet irradiation in a state where the lyotropic liquid crystalline compound is aligned. Manufacturing method of polarizing element.   The coating liquid containing the lyotropic liquid crystalline compound further comprises a polymerizable compound, and includes a step of polymerizing and fixing by irradiation of heat or ultraviolet rays in a state where the lyotropic liquid crystalline compound is aligned. The manufacturing method of the polarizing element in any one of.   A liquid crystal display element comprising at least one liquid crystal cell and at least one polarizing element according to claim 1.   8. The liquid crystal display according to claim 7, wherein the liquid crystal cell is a vertical alignment mode liquid crystal cell in which liquid crystal is aligned substantially vertically when no voltage is applied and is aligned substantially horizontally when a voltage is applied. element.   The liquid crystal cell has an electrode on at least one of the liquid crystal cells, the liquid crystal is aligned parallel to the substrate between a pair of transparent substrates in parallel with each other, and the direction of the molecular major axis of the liquid crystal is The liquid crystal display element according to claim 7, wherein the liquid crystal display element is configured to change in a plane parallel to the substrate by a change in voltage applied to the liquid crystal cell.

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