JP3174367B2 - Laminated wave plate and circularly polarizing plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a laminated wave plate that provides a predetermined phase difference such as 波長 wavelength or １ ／ wavelength, and a circularly polarizing plate that prevents reflection over a wide wavelength range.

[0002]

2. Description of the Related Art Conventionally, a half-wave plate and a quarter-wave plate using one stretched film have been known. However, there is a problem that the phase difference differs for each wavelength, and a wavelength that can function as a half-wave plate or a quarter-wave plate is limited to a specific wavelength.

That is, for example, in the case of a device that functions as a quarter-wave plate for light having a wavelength of 550 nm, the wavelength is 4
It does not function as a quarter-wave plate for light of 50 nm or 650 nm. For example, when a circularly polarizing plate is adhered to a polarizing plate and used as an antireflection filter for suppressing surface reflection of a display or the like, the wavelength is 550.
It does not exhibit sufficient anti-reflection function for light that is not nm,
In particular, there is a problem that a display or the like looks blue due to poor antireflection function for blue light.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a wavelength plate which can function almost as a half-wave plate or a quarter-wave plate over a wide wavelength range such as the entire visible light range, and a broadband antireflection film. The aim is to develop an excellent circularly polarizing plate.

[0005]

The present invention SUMMARY OF THE INVENTION may, Ri a plurality of oriented films giving a retardation of 1/2 wavelength with respect to monochromatic light greens are laminated by intersecting their optical axis, as a whole 1 /
Laminated wave plate characterized that you function as half-wave plate,
And a plurality of stretched films are laminated with their optical axes intersecting with each other, and the stretched films are に 対 し て to monochromatic light.
And that provides a phase difference of wavelength, I Do from a combination of those giving a phase difference of 1/4 wavelength, the whole as a quarter-wave
Laminated wave plate characterized that you function as a plate, as well as to provide a circularly polarizing plate, characterized by comprising a laminate of the laminated wave plate and polarizing plate using the quarter wave film of the is there.

[0006]

A plurality of stretched films which give a phase difference of ２ wavelength or 波長 wavelength to monochromatic light are laminated with their optical axes crossing each other to obtain a refractive index difference of birefringent light (光
The wavelength dispersion of the retardation defined by the product (△ nd) of n) and the thickness (d) can be arbitrarily controlled by superimposing or adjusting the chromatic dispersion, and the chromatic dispersion is suppressed while controlling the phase difference as a whole to a predetermined value. Thus, a wave plate exhibiting a predetermined phase difference over a wide wavelength range can be obtained.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The laminated wave plate according to the present invention has a 1 /
A plurality of stretched films giving a phase difference of two wavelengths are laminated with their optical axes crossing each other to form a half-wave plate as a whole.
It works . FIG. 1 shows an example thereof. 1,3
Is a stretched film that gives a half-wave retardation, and 2 is a transparent adhesive layer. The number of layers of the stretched film is arbitrary, but 2 to 5 layers are generally used from the viewpoint of light transmittance and the like.

The crossing angle of the optical axis of each stretched film to obtain a half-wave plate can be, for example, one calculated by the following equation as a basic example. That is, when the number of layers is N and the angle of the output linear polarization direction (θ) after transmission through the wavelength plate is θ with the incident linear polarization direction as a reference (0 °), the angle θ _K of each half-wave film is , Θ _K = (2K−1) ·
θ / 2N (where K is an integer value of 1 to N).

On the other hand, another laminated wave plate of the present invention comprises a plurality of stretched films formed by a combination of a stretched film which gives a phase difference of 波長 wavelength to a monochromatic light and a stretched film which gives a phase difference of １ ／ wavelength. Using a film, the optical axes of the stretched films are crossed and laminated, and as a whole, as a 1/4 wavelength plate
It works . An example is shown in FIG. 1, 3 is a stretched film giving a half-wave retardation, 4 is 1/4
The stretched film 2 for giving a wavelength phase difference is a transparent adhesive layer.

The conditions for obtaining a quarter-wave plate are as follows: a stretched film that gives a half-wave retardation to monochromatic light;
Using a stretched film giving a / 4 wavelength retardation,
And the optical axes of the stretched films to be laminated are crossed.

Regarding the use of the above-mentioned stretched film which gives a phase difference of 波長 wavelength to the monochromatic light and the stretched film which gives a phase difference of 波長 wavelength, the number of layers of the stretched film is arbitrary. Generally, two to five sheets are stacked in terms of light transmittance and the like. Further, the arrangement positions of the stretched film that gives a retardation of １ ／ wavelength and the stretched film that gives a retardation of 波長 wavelength are also arbitrary.

In the above, a phase difference of 1/4 wavelength is given.
Outgoing side of laminated wave plate using one stretched film
As an example of the case of disposing at the end, the optical axis of each stretched film is
The relationship between the crossing angle and the direction (θ) of polarized light exiting each stretched film
The relation is expressed by the following equation. That is, the phase difference of 1/2 wavelength is
Let n be the number of stretched films used and give them λ / 2
(1, 2,... N) with reference to the incident linear polarization direction
(0 °) and the stacking angle of each λ / 2 (1, 2,... N)
Degree θ₁, Θ_Two, ... θ_nThen, the stacking angle = 2 (θ₁+ Θ_Two+ ... + θ_n-1) + Θ_n  The direction of polarized light leaving each λ / 2 plate = 2 (θ₁+ Θ_Two+
... + θ_n) And the phase difference of 1/4 wavelength
The stretched film to be applied is laminated at an angle of 45 degrees.
A circularly polarized light is obtained.

The above relationship is shown in the following table, taking as an example the case where three stretched films (λ / 2 (1, 2, 3)) giving a retardation of 波長 wavelength are used. Here, λ / 4 represents a stretched film that gives a retardation of 波長 wavelength.

In the present invention, 1 is used for monochromatic light.
A stretched film giving a phase difference of ／ wavelength or ４ wavelength can be obtained, for example, by a method of stretching a polymer film uniaxially or biaxially.

The type of the polymer forming the stretched film is not particularly limited, and those having excellent transparency are preferably used. Examples thereof include polycarbonate polymers, polyester polymers, polysulfone polymers, polyethersulfone polymers, polystyrene polymers,
Examples include polyolefin polymers, polyvinyl alcohol polymers, cellulose acetate polymers, polyvinyl chloride polymers, polymethyl methacrylate polymers, and the like.

The circularly polarizing plate of the present invention is obtained by laminating a laminated wave plate using the above-mentioned quarter-wave film and a polarizing plate. An example is shown in FIG. 5 is a polarizing plate, 6 is a laminated wave plate, and 2 is a transparent adhesive layer. The formation of a circular polarizing plate
It can be performed by crossing the polarizing plate (5) at the above-mentioned lamination angle. At this time, the direction of the circularly polarized light (counterclockwise or clockwise circularly polarized light) can be converted by changing the transmission axis of the polarizing plate by 90 degrees.

An appropriate polarizing plate can be used for forming the circularly polarizing plate, and there is no particular limitation. In general, a film made of a hydrophilic polymer such as polyvinyl alcohol is stretched by treating with a dichroic dye such as iodine, or a film obtained by treating a plastic film such as polyvinyl chloride to orient polyene. Or a film obtained by covering the polarizing film with a sealing film and protecting it.

The lamination of the stretched film and the lamination of the laminated wave plate and the polarizing plate can be performed using, for example, a transparent adhesive or an adhesive. There is no particular limitation on the type of the adhesive or the like. From the viewpoint of preventing a change in the optical characteristics of the constituent members, it is preferable that a high-temperature process is not required for curing and drying, and that a long curing process and a drying time are not required. The laminated wave plate and the circularly polarizing plate are provided with an adhesive layer or the like as necessary, and have a form that can be adhered to an adherend such as a liquid crystal cell.

The laminated wave plate as the half-wave plate or quarter-wave plate of the present invention can be used for various applications such as an anti-reflection filter or an anti-glare filter and a liquid crystal projector.

Reference Example 1 A polycarbonate film having a thickness of 50 μm is stretched by 5% at 150 ° C. to give a λ / 2 stretched film which gives a phase difference of 波長 wavelength to light having a wavelength of 550 nm based on birefringent light. Obtained.

Reference Example 2 A polycarbonate film having a thickness of 50 μm was stretched by 2.5% at 150 ° C., and the wavelength was 550 nm based on birefringent light.
A λ / 4 stretched film giving a 差 wavelength retardation to the above light was obtained.

Example 1 Two λ / 2 stretched films obtained in Reference Example 1 were laminated via an acrylic pressure-sensitive adhesive so that their optical axes (stretching axes) crossed each other at an angle of 25 degrees. A half-wave plate was obtained.

Example 2 Three λ / 2 stretched films obtained in Reference Example 1 were laminated via an acrylic adhesive so that their optical axes crossed at an angle of 30 degrees between the upper and lower sides. / 2 wavelength plate was obtained.

Example 3 Two λ / 2 stretched films obtained in Reference Example 1 were laminated via an acrylic adhesive so that their optical axes crossed at an angle of 27.7 degrees. The obtained λ / 4 stretched film is laminated via an acrylic pressure-sensitive adhesive so that its optical axis intersects the optical axis of the upper λ / 2 stretched film at an angle of 66 degrees, and the λ / 4 stretched film according to the present invention is used. I got a board.

Example 4 A polarizing film (NPF-N) was applied to the 1/4 wavelength plate obtained in Example 3.
G1225DU, manufactured by Nitto Denko Corporation) via an acrylic pressure-sensitive adhesive to obtain a circularly polarizing plate of the present invention. The lamination is
The optical axis of the λ / 4 stretched film and the transmission axis of the polarizing film are 1
The crossing was performed at an angle of 00.2 degrees.

Comparative Example 1 One of the λ / 2 stretched films obtained in Reference Example 1 was
It was used as a / 2 wavelength plate.

Comparative Example 2 One of the λ / 4 stretched films obtained in Reference Example 2 was
It was used as a 波長 wavelength plate.

Comparative Example 3 A circularly polarizing plate was obtained in the same manner as in Example 4 except that the quarter-wave plate obtained in Comparative Example 2 was used. However, the intersection angle between the optical axis of the quarter-wave plate and the transmission axis of the polarizing film was 45 degrees.

Evaluation Test Broad-Bandwidth of 1/2 Wavelength Plate The half-wavelength plates obtained in Examples 1 and 2 and Comparative Example 1 were arranged between polarizing plates arranged in crossed Nicols, and the spectral spectrum was examined. Note that the arrangement of the half-wave plate is such that the optical axes of the two λ / 2 stretched films are 22.5 degrees and 47.5 degrees with respect to the transmission axis of the incident-side polarizing plate in Example 1, respectively. Thus, in Example 2, the optical axes of the three λ / 2 stretched films were set to 15 degrees, 45 degrees, and 75 degrees, respectively, and in Comparative Example 1, they were set to 45 degrees.

FIG. 4 shows the results. Thus, the wavelength range in which the phase difference of about 波長 wavelength is provided is only around 550 nm in Comparative Example 1, whereas the wavelength range in Examples 1 and 2 is
It can be seen that the wavelength ranges from 450 to 700 nm.

Broadband properties of quarter-wave plate The quarter-wave plates obtained in Example 3 and Comparative Example 2 were arranged between polarizing plates arranged in crossed Nicols, and the spectrum was examined. Note that the arrangement of the quarter-wave plate is such that the optical axes of the two λ / 2 stretched films are 6.5 degrees and 34.2 degrees with respect to the transmission axis of the incident-side polarizing plate in Example 3, respectively. The optical axis of the λ / 4 stretched film was set to 100.2 degrees, and in Comparative Example 2, the optical axis was set to 45 degrees.

The results are shown in FIG. From this, it can be seen that the wavelength range in which the phase difference of approximately 波長 wavelength is provided is only around 550 nm in Comparative Example 2, whereas the wavelength range in Example 3 is as wide as 450 to 700 nm.

Broadband Properties of Antireflection The circularly polarizing plates obtained in Example 4 and Comparative Example 3 were placed on a light reflecting plate, and the light transmission state was examined. As a result, in Example 4, all of the visible light was shielded and black. On the other hand, in Comparative Example 3, it looked blue, and there was no light-blocking effect for blue light.

[0034]

According to the present invention, it is possible to obtain a wave plate having a small change in the phase difference due to a change in the wavelength.
A half-wave plate and a quarter-wave plate can be obtained. Also,
By using such a quarter-wave plate, a circularly polarizing plate useful as a broadband antireflection filter for substantially preventing reflection of light in the visible region or the like can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a half-wave plate of an embodiment.

FIG. 2 is a cross-sectional view illustrating a quarter-wave plate of another embodiment.

FIG. 3 is a cross-sectional view illustrating a circularly polarizing plate.

FIG. 4 is a graph showing the spectrum of a half-wave plate.

FIG. 5 is a graph showing the spectrum of a quarter-wave plate.

[Explanation of symbols]

 1: 3: stretched film giving a phase difference of 1/2 wavelength 2: adhesive layer 4: stretched film giving a phase difference of 1/4 wavelength 5: polarizing plate 6: 1/4 wavelength plate

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-120804 (JP, A) JP-A-1-130121 (JP, A) Gaudefroy, SUR LA ROTATION QUASI-A CHROMATIQUE DES VI BARATIONS LUMINUS ES RECTILIGNES AU MOYEN DE LAMES CRISTALLIES BIREFRING GENTS. Soc. Frances. Min. , France, 1943, 66, pp. 305-314 (58) Fields surveyed (Int. Cl. ⁷ , DB name) G02B 5/30

Claims (3)

(57) [Claims] 1. A plurality of oriented films giving a retardation of 1/2 wavelength with respect to monochromatic light by intersecting their optical axes Ri name and laminated, Rukoto to function as a whole as a half-wave plate The laminated wave plate characterized by the above. 2. A plurality of stretched films which are laminated with their optical axes crossing each other, wherein the stretched film gives a phase difference of の wavelength to monochromatic light, Do from the combination of the things that gives the phase difference, as a whole
Laminated wave plate characterized that you function as a quarter-wave plate. 3. A circularly polarizing plate comprising a laminate of the laminated wave plate according to claim 2 and a polarizing plate.