JPH1152131A - Phase difference plate and polarizing element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase difference plate having excellent mass productivity advantageous as a wide-band wavelength plate to generate a uniform phase difference in a visible light wavelength region at the time of creating linearly polarized light, circularly polarized light and elliptically polarized light by an optical element, polarizing element, optical analyzer, optical measuring instrument and optical experiment, etc. SOLUTION: This phase difference plate consists of liquid crystal molecules which are laminated in the bearing orthogonal with the respective delay axis of a double refractive medium A of a wavelength dispersion value αA and a double refractive medium B of a wavelength dispersion value αB of αA<αB in the relation of the wavelength dispersion value α (α=Δn(450 nm)/Δn(650 nm)) of a double refractive index Δn and in which at least one of the double refractive media has a homogeneously oriented molecule orientation state. The relation between the phase difference RA of the double refractive medium A and the phase difference RB of the double refractive medium B is RA>RB and the wavelength dispersion value α is smaller than 1. As a result, the nearly uniform phase difference may be generated in correspondence to all the wavelengths of the visible light region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element, a polarizing element, an optical analyzer, an optical measuring apparatus, an optical experiment, and the like, for producing linearly polarized light, circularly polarized light, and elliptically polarized light in a uniform wavelength range in the visible light wavelength region. The present invention relates to a retardation plate excellent in mass productivity, which is advantageous as a broadband wavelength plate for generating a retardation.

[0002]

2. Description of the Related Art A retardation plate is obtained by stretching a thin plate made of an inorganic material such as calcite, mica, and quartz or a polymer film having a high intrinsic birefringence. Converting linearly polarized light to circularly polarized light 1
There are a 波長 wavelength plate (hereinafter abbreviated as a λλ plate) and a 波長 wavelength plate (hereinafter abbreviated as a 板 λ plate) that converts a polarization oscillation plane of linearly polarized light by 90 °.

[0003] In the case of monochromatic light, these retardation plates are adjusted to a phase difference of 1 / 4λ or 1 / 2λ of the light wavelength.
In the case of white light, which is a composite wave in which light rays in the visible light region are mixed, the distribution of the polarization state at each wavelength occurs due to the wavelength dispersion of the phase difference of the material constituting the phase difference plate, and the light is converted into colored polarized light. Is done. Further, in the case of a wavelength plate, it is necessary to prepare a retardation plate adjusted according to the wavelength to be applied from the wavelength dispersibility of the material, so that a wavelength plate for each wavelength is required. That is, in the conventional retardation plate, there are problems that the cost is increased because a wavelength plate is prepared for each light beam wavelength to be used, and that application to white light is unsuitable.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mass-producing optical system having a wavelength dispersibility such that an optical phase difference at all wavelengths of visible light generates a uniform phase difference regardless of the wavelength. To provide an excellent retardation plate.

[0005]

In order to achieve the above object, the retardation plate of the present invention has a wavelength dispersion value α (α = Δn (450 nm) / Δn) of the birefringence index Δn.
(650 nm)) is a wavelength dispersion value α in which α _A <α _B
In the phase difference plates are laminated in the orientation orthogonal to each slow axis of the birefringent medium B of the birefringent medium A and the wavelength dispersion value alpha _B of _A, in the molecular alignment state at least one of homogeneously aligned among the birefringent medium a liquid crystal molecules, the relationship of the phase difference R _B of the phase difference R _a and birefringent medium B of the birefringent medium a R _a> R _B
Wherein the wavelength dispersion value α of the retardation plate in which the birefringent medium A and the birefringent medium B are laminated is smaller than 1.

Further, it is preferable that at least one liquid crystal molecule constituting the birefringent medium has at least one of an acrylate group, a methacrylate group, a vinyl ether group and an epoxy group as a polymerization functional group. Features.

Further, at least one liquid crystal molecule constituting the birefringent medium is in a molecular alignment state of a nematic phase.

Further, at least one liquid crystal molecule constituting the birefringent medium is in a molecular orientation state of a smectic phase.

[0009] The thin film constituting the birefringent medium is characterized by comprising at least a mixture of liquid crystal molecules and other organic compounds.

[0010] The liquid crystal phase of at least one of the liquid crystal molecules constituting the birefringent medium is characterized in that the alignment state is fixed by photopolymerization.

[0011] The present invention is also characterized in that at least one layer of an alignment film of inorganic or organic molecules for controlling the molecular alignment state of at least one liquid crystal molecule constituting the birefringent medium is used.

Further, characterized in that the phase difference R is _{(R A -R B) = 1} / 4λ plate which is adjusted to lambda / 4.

Further, the present invention is characterized in that the phase difference R is a half λ plate adjusted to (R _A -R _B ) = λ / 2.

Also, a part that divides a part of the unpolarized light into two polarized lights whose polarization planes are orthogonal to each other, and that one of the two polarized lights is changed to match the polarization plane of the polarized light whose polarization plane is not changed. In a polarizing element having a modulating unit to be used, the retardation plate of the present invention may be used as the modulating unit.

A unit for converting non-polarized light into polarized light is
A sheet-shaped polarizing element that is continuously processed, wherein the unit changes a part of the unpolarized light into reflected light and transmitted light whose polarization planes are orthogonal to each other, and changes a polarization plane of the reflected light. In a sheet-like polarizing element having a modulation section that is made to coincide with the polarization plane of transmitted light, the retardation plate of the present invention may be used as the modulation section.

Further, a cube-type polarizing beam splitter and a light exiting surface on the reflected light side of the polarizing beam splitter are provided on the surface.
A 偏光 wavelength plate is used as a 反射 wavelength plate in a light reflecting plate bonded and bonded so as to sandwich a 波長 wavelength plate and at least two or more right angle prisms bonded together with the reflecting plate and the polarizing beam splitter therebetween. It is preferable to use the phase difference plate of the present invention.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When linearly polarized white light is incident on the retardation plate of the present invention, a wavelength dispersion value α (α =
Δn (450 nm) / Δn (650 nm)) is α
_Since the birefringent media of A and B satisfying _A <α _B are laminated so that the slow axes are perpendicular to each other, α _{A having} a small wavelength dispersion is used.
Is canceled out by the phase difference caused by the material having the property of α _B having large wavelength dispersion. At this time, α _B
Since the phase difference is canceled by the material having the characteristic described above, the phase difference generated at a shorter wavelength has a larger amount of the canceled phase difference.

Since the relationship between the birefringent media is R _A > R _B , the phase difference to be emitted is emitted as polarized light having a smaller phase difference as the wavelength becomes shorter. In other words, the retardation plate of the present invention produces a smaller phase difference as the wavelength of the incident light is shorter, and produces a larger phase difference as the wavelength of the incident light is longer. Therefore, the wavelength dispersion characteristic of the retardation plate according to the present invention tends to monotonically increase as the wavelength becomes longer, and the optical phase difference at all wavelengths of visible light becomes uniform regardless of the wavelength. Since the retardation plate of the present invention has,
Polarized light incident as white light also has a uniform phase difference in the visible light region and can be obtained as white polarized light.

[0019]

Next, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples. The optical properties of the retardation plate of the present invention were measured by the following methods. (1) Phase difference and slow axis The optical phase difference and the slow axis at a wavelength of 550 nm were measured using a polarizing microscope BH2 manufactured by Olympus Optical Co., Ltd. and a Berek compensator. (2) Wavelength Dispersion Value The optical phase difference in a wavelength range of 450 nm to 754 nm was measured using KOBRA manufactured by Oji Scientific Instruments.

Example A polyethylene-vinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., EF-F; hereinafter abbreviated as EVOH) was uniaxially stretched at 180 ° C. at an atmosphere temperature not lower than the thermal deformation temperature, and the light was irradiated at 550 nm. The phase difference was adjusted to 550 nm. In the stretched EVOH film, the slow axis coincided with the stretching direction, and the wavelength dispersion value α was 1.004.

An oriented film (manufactured by Sumitomo Bakelite Co., Ltd., CRD-8616) is flexographically printed on the stretched EVOH film,
After an imidation treatment in an atmosphere of 0 ° C. for 2 hours, EV
Rubbing treatment was performed in a direction perpendicular to the OH stretching direction to form an alignment film.

A coating solution prepared by dissolving 1.98 g of a nematic UV-curable liquid crystal (UCL-002, manufactured by Roddick) and 0.02 g of a photopolymerization initiator (Dilka Cure 651, manufactured by Ciba-Geigy) in 3 g of methyl ethyl ketone was prepared as follows. EV with alignment treatment
After coating and drying the OH film with a bar coater, 1 mW /
UV irradiation was performed under the conditions of cm ² and 240 seconds to obtain a birefringent thin film. The UV-cured liquid crystal birefringent thin film has a thickness of 2.8 μm and a thickness of 5 μm.
The phase difference was 275 nm for a 50 nm light beam. Also, the slow axis of birefringence coincides with the rubbing direction of the alignment film,
The wavelength dispersion value α was 1.439.

UV is applied to the oriented EVOH film
The retardation plate coated with the cured liquid crystal and cured has the slow axis of birefringence of each layer perpendicular to the retardation plate, and the retardation of the laminated retardation plate is 550 nm.
Is 275 nm and the chromatic dispersion value is 0.66
Nine.

As a result of measuring the optical retardation in the wavelength range of 450 nm to 754 nm, the optical function of the 1 / 2λ plate produced from the UV-curable liquid crystal / EVOH laminated type retardation plate according to the present invention was 450 nm to 650 nm. Phase shift of 5% or less in the wavelength range of
Function shown.

(Comparative Example) A retardation plate made of an existing material is shown as a comparative example.

Polycarbonate (Pokalon, manufactured by Lonza)
Hereinafter, abbreviated as PC) is defined as an ambient temperature equal to or higher than the heat distortion temperature.
Uniaxially stretching at 75 ° C., 275 n for 550 nm light
The phase difference was adjusted to m. In the stretched PC film, the slow axis coincided with the stretching direction, and the wavelength dispersion value α was 1.098.

As a result of measuring the optical retardation in the wavelength range of 450 nm to 754 nm, the optical function of the 1 / 2λ plate made from the retardation plate of the stretched PC film was 450 nm.
In the wavelength range from 650 nm to 650 nm, the phase difference was 28%, and the 1 / 2λ function was greatly reduced.

[0028]

As described above, by using the retardation plate of the present invention, the optical phase difference at all wavelengths in the visible light range becomes almost uniform irrespective of the light wavelength. Not only is it easy to obtain, but when obtaining a wave plate, there is no need for a wave plate for each applied light wavelength, and it has the advantage that it can be applied to the entire wavelength range with one wave plate, and is excellent in mass productivity. A phase difference plate can be provided. The retardation plate of the present invention takes advantage of the above characteristics, various display elements that require polarized light,
In particular, it can be applied to a wide range of applications, such as a liquid crystal display device, an optical switch, an optical filter, and various optical measuring devices using the same as a constituent element.

[Brief description of the drawings]

FIG. 1 Wavelength dispersion characteristics of a retardation plate in the visible light region

FIG. 2 shows a retardation characteristic in a visible light region of a half-wave plate produced by the retardation plate of the present invention.

Claims (12)

[Claims] 1. A wavelength dispersion value α (α = Δn) of a birefringence index Δn.
(450 nm) / Δn (650 nm)) is α _A <
In the phase difference plates are laminated in the orientation orthogonal to each slow axis of the birefringent medium B of alpha _B is a wavelength dispersion value alpha _A birefringent medium A and the wavelength dispersion value alpha _B of at least one of the birefringent medium a liquid crystal molecules in homogeneous alignment molecular orientation state, a is R _a> R _B relationship of the phase difference R _B of the phase difference R _a of the birefringent medium a and birefringence medium B, the birefringent medium a and birefringence A retardation plate wherein the wavelength dispersion value α of the retardation plate on which the medium B is laminated is smaller than 1. 2. A liquid crystal molecule in at least one molecular orientation state that constitutes a birefringent medium has at least one of an acrylate group, a methacrylate group, a vinyl ether group, and an epoxy group as a polymerizable functional group. The phase difference plate according to claim 1, wherein 3. The retardation plate according to claim 1, wherein at least one liquid crystal molecule constituting the birefringent medium is in a molecular alignment state of a nematic phase. 4. The retardation plate according to claim 1, wherein at least one liquid crystal molecule constituting the birefringent medium is in a molecular alignment state of a smectic phase. 5. The retardation plate according to claim 1, wherein the thin film constituting the birefringent medium is composed of a mixture of at least liquid crystal molecules and another organic compound. 6. The retardation plate according to claim 1, wherein the molecular orientation state of the liquid crystal phase of at least one liquid crystal molecule constituting the birefringent medium is fixed by photopolymerization. 7. The retardation plate according to claim 1, wherein at least one alignment film of inorganic or organic molecules for controlling the molecular alignment state of at least one liquid crystal molecule constituting the birefringent medium is used. . 8. The phase difference plate according to claim 1, wherein the phase difference R is a ４λ plate adjusted to (R _A −R _B ) = λ / 4. 9. The phase difference R is (R _A -R _B) = retardation plate according to claim 1, characterized in that the 1/2 [lambda] plate which is adjusted to lambda / 2. 10. A part that divides a part of unpolarized light into two polarized lights whose polarization planes are orthogonal to each other, and one of the two polarized lights.
In a polarizing element having a modulator that changes two polarization planes to match the polarization plane of polarized light whose polarization plane does not change,
A polarizing element comprising the phase difference plate according to claim 1 as a modulator. 11. A unit for converting non-polarized light into polarized light, wherein the unit is a continuously processed sheet-like polarizing element, wherein the unit is configured to reflect a part of the non-polarized light to reflected light whose polarization plane is orthogonal to each other. 10. The position of claim 1 or 9, wherein the sheet-like polarizing element has a portion for splitting the transmitted light and a modulator for changing the polarization plane of the reflected light to match the polarization plane of the transmitted light. A sheet-like polarizing element having a phase difference plate. 12. A cube-type polarizing beam splitter, and an output surface on the reflected light side of the polarizing beam splitter is provided.
A 偏光 wavelength plate is used as a 反射 wavelength plate in a light reflecting plate bonded and bonded so as to sandwich a 波長 wavelength plate and at least two or more right angle prisms bonded together with the reflecting plate and the polarizing beam splitter therebetween. A polarizing element comprising the retardation plate according to claim 1.