JPH05100114A - Laminated wavelength plate and circularly polarizing plate - Google Patents

Abstract

PURPOSE:To obtain the laminated wavelength plate which lessens a change in the phase difference according to a change in wavelength and gives the prescribed phase difference of 1/2 wavelength, 1/4 wavelength, etc., over a wide wave length region and the circularly polarizing plate useful as an antireflection filter which prevents reflection over a wide wavelength region, such as visible region. CONSTITUTION:This laminated wavelength plate is constituted by laminating plural stretched films 1, 3 which give the phase difference of a 1/2 wavelength to monochromatic light by intersecting the optical axes thereof. The laminated wavelength plate is otherwise constituted by laminating the plural stretched films by intersecting the optical axes thereof and consists of a combination of the stretched film which gives the phase difference of 1/2 wavelength to the monochromatic light and the stretched film which gives the phase difference of a 1/4 wavelength thereto. This circularly polarizing plate consists of the laminate of the laminated wavelength plate formed by using the above-mentioned 1/4 wavelength film and the polarizing plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to a wide wavelength range.
The present invention relates to a laminated wave plate that gives a predetermined phase difference such as / 2 wavelength or ¼ 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, the phase difference is different for each wavelength, and there is a problem that the wavelength that can function as a ½ wavelength plate or a ¼ wavelength plate is limited to a specific wavelength.

That is, for example, in the case of a plate 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. Therefore, 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.
Does not exhibit sufficient antireflection function for light that is not nm,
In particular, there is a problem that the display and the like look blue due to its poor antireflection function for blue light.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a wavelength plate that can substantially function 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 property of antireflection. The purpose is to develop an excellent circularly polarizing plate.

[0005]

The present invention is characterized in that a plurality of stretched films which give a phase difference of ½ wavelength to monochromatic light are laminated with their optical axes intersecting each other. A wave plate and a plurality of stretched films are laminated with their optical axes intersecting each other, and the stretched film gives a phase difference of ½ wavelength to a monochromatic light and a phase difference of ¼ wavelength. And a circularly polarizing plate comprising a laminated body of a laminated wavelength plate and a polarizing plate using the above-mentioned quarter wavelength film. To do.

[0006]

The refractive index difference (Δ) of birefringent light is obtained by laminating a plurality of stretched films that give a phase difference of ½ wavelength or ¼ wavelength to monochromatic light with their optical axes intersecting.
The wavelength dispersion of the retardation defined by the product (Δnd) of n) and the thickness (d) can be superimposed or adjusted to control it arbitrarily, and suppress the wavelength dispersion while controlling the phase difference as a whole to a predetermined value. Thus, it is possible to obtain a wave plate exhibiting a predetermined phase difference over a wide wavelength range.

[0007]

EXAMPLES The laminated wave plate of the present invention is 1 /
A plurality of stretched films that give a retardation of two wavelengths are laminated with their optical axes intersecting. An example is shown in FIG. Stretched films 1 and 3 give a retardation of ½ wavelength, and 2 is a transparent adhesive layer. The number of laminated stretched films is arbitrary, but from the viewpoint of light transmittance and the like, generally 2 to 5 laminated layers are used.

The crossing angle of the optical axes of the respective stretched films for obtaining the half-wave plate can be calculated by the following formula as a basic example. That is, when the number of laminated layers is N and the angle of the outgoing linearly polarized light direction (θ) after passing through the wave plate is θ with reference to the incident linearly polarized light direction (0 °), the angle θ _K of each ½ wavelength 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 stretched film and a stretched film which give a phase difference of ½ wavelength to monochromatic light.
A plurality of stretched films are used in combination with a stretched film that gives a retardation of / 4 wavelength, and the stretched films are laminated with their optical axes intersecting each other. An example thereof is shown in FIG. Stretched films 1 and 3 give a retardation of 1/2 wavelength, 4 stretched films give a retardation of 1/4 wavelength, 2
Is a transparent adhesive layer.

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

Regarding the point of using the stretched film which gives a retardation of ½ wavelength and the stretched film which gives a retardation of ¼ wavelength to the monochromatic light, the number of laminated stretched films is arbitrary. From the viewpoint of light transmittance and the like, a stack of 2 to 5 sheets is generally used. Further, the positions where the stretched film that gives a retardation of ½ wavelength and the stretched film that gives a retardation of ¼ wavelength are arbitrary.

In the above, a phase difference of 1/4 wavelength is given.
The stretched film is used as a stretched film
Taking the case of arranging at the edge as an example,
The relationship between the crossing angle and the direction of polarization (θ) exiting each stretched film
The relation is expressed by the following equation. That is, the phase difference of 1/2 wavelength
Let n be the number of stretched films to be used and give them λ / 2.
Expressed as (1, 2, ... n), the incident linear polarization direction is the reference
(0 °) and stacking angle of each λ / 2 (1, 2, ... n)
Degree is θ₁, Θ₂, ... θ_nThen, stacking angle = 2 (θ₁+ Θ₂+ ... + θ_n-1) + Θ_n  Direction of polarized light exiting each λ / 2 plate = 2 (θ₁+ Θ₂+
... + θ_n), And the phase difference of 1/4 wavelength is added to it.
By laminating the stretched films to give at an angle of 45 degrees
A circularly polarized light is obtained.

The above relationship is shown in the following table by taking as an example the case where three stretched films (λ / 2 (1,2,3)) which give a retardation of ½ wavelength are used. In addition, λ / 4 represents a stretched film that gives a retardation of ¼ wavelength.

1 for monochromatic light used in the present invention
The stretched film that gives a retardation of / 2 wavelength or ¼ wavelength can be obtained by, for example, a method of stretching a polymer film uniaxially or biaxially.

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

The circularly polarizing plate of the present invention is a laminate of a laminated wave plate using the above-mentioned quarter wavelength film and a polarizing plate. An example thereof is shown in FIG. Reference numeral 5 is a polarizing plate, 6 is a laminated wave plate, and 2 is a transparent adhesive layer. The circular polarizing plate is formed by
It can be performed by intersecting with the polarizing plate (5) at the above-mentioned stacking angle. At this time, the direction of 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. Generally, a film made of a hydrophilic polymer such as polyvinyl alcohol is treated with a dichroic dye such as iodine and stretched, or a plastic film such as polyvinyl chloride is oriented with polyene. Or a polarizing film covered with a sealing film for protection.

The stretched films and the laminated wave plate and the polarizing plate can be laminated using, for example, a transparent adhesive or pressure-sensitive adhesive. There is no particular limitation on the type of the adhesive or the like. From the viewpoint of preventing changes in the optical characteristics of the constituent members, those that do not require a high temperature process during curing or drying are preferable, and those that do not require a long curing process or drying time are desirable. Further, the laminated wave plate and the circularly polarizing plate are provided with an adhesive layer or the like if necessary, and are in a form capable of being adhered to an adherend such as a liquid crystal cell.

The laminated wave plate as the ½ wave plate or the ¼ wave plate of the present invention can be used for various applications such as an antireflection filter or an antiglare filter and a liquid crystal projector.

Reference Example 1 A polycarbonate film having a thickness of 50 μm was stretched by 5% at 150 ° C. to obtain a λ / 2 stretched film which gives a phase difference of ½ wavelength with respect 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 that gives a phase difference of ¼ wavelength with respect 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) intersect each other at an angle of 25 degrees, and according to the present invention. A half-wave plate was obtained.

Example 2 The three λ / 2 stretched films obtained in Reference Example 1 were laminated with an acrylic pressure-sensitive adhesive so that their optical axes intersected at an angle of 30 degrees between the top and bottom, and 1 according to the present invention was used. A half wave plate was obtained.

Example 3 Two λ / 2 stretched films obtained in Reference Example 1 were laminated with an acrylic pressure-sensitive adhesive so that their optical axes intersect at an angle of 27.7 degrees, and further in Reference Example 2. The obtained λ / 4 stretched film was laminated via an acrylic pressure-sensitive adhesive so that the optical axis thereof intersected with the optical axis of the upper λ / 2 stretched film at an angle of 66 degrees, and the quarter wavelength according to the present invention was laminated. I got a board.

Example 4 A polarizing film (NPF-) was added to the quarter-wave plate obtained in Example 3.
G1225DU, manufactured by Nitto Denko Corporation) was laminated via an acrylic adhesive to obtain a circularly polarizing plate of the present invention. The stack 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 used as is.
It was used as a half wave plate.

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

Comparative Example 3 A circularly polarizing plate was obtained in the same manner as in Example 4 except that the one obtained in Comparative Example 2 was used as the 1/4 wavelength plate. However, the crossing angle between the optical axis of the quarter-wave plate and the transmission axis of the polarizing film was 45 degrees.

Evaluation Test Broad band property of 1/2 wavelength plate The 1/2 wavelength plates obtained in Examples 1 and 2 and Comparative Example 1 were placed between polarizing plates arranged in crossed Nicols to examine the spectral spectrum. In addition, the arrangement of the ½ wavelength plate is such that the optical axes of the two λ / 2 stretched films in Example 1 are 22.5 degrees and 47.5 degrees with respect to the transmission axis of the incident side polarizing plate, respectively. As described above, 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.

The above results are shown in FIG. From this, the wavelength range that gives a phase difference of approximately ½ wavelength is only in the vicinity of the wavelength of 550 nm in Comparative Example 1, whereas in Examples 1 and 2,
Shows that the wavelength covers a wide range of 450 to 700 nm.

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

The above results are shown in FIG. From this, it can be seen that the wavelength range that gives a phase difference of approximately ¼ wavelength is only in the vicinity of the wavelength of 550 nm in Comparative Example 2, whereas it extends to a wide range of 450 to 700 nm in Example 3.

Broadband property 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 blocked and it was in a black state. On the other hand, Comparative Example 3 looked blue and had no light-shielding effect on bluish light.

[0034]

According to the present invention, it is possible to obtain a wave plate in which the change in the phase difference with the change in the wavelength is small, and the wavelength band is wide.
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 that substantially prevents reflection of light in the visible range can be obtained.

[Brief description of drawings]

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

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 a spectrum of a ½ wavelength plate.

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

[Explanation of symbols]

 1,3: Stretched film giving a retardation of 1/2 wavelength 2: Adhesive layer 4: Stretched film giving a retardation of 1/4 wavelength 5: Polarizing plate 6: 1/4 wavelength plate

Claims (3)

[Claims] 1. A laminated wave plate comprising a plurality of stretched films which give a phase difference of ½ wavelength to monochromatic light and are laminated with their optical axes intersecting each other. 2. A plurality of stretched films are laminated with their optical axes intersecting each other, and the stretched film gives a phase difference of ½ wavelength to monochromatic light and a position of ¼ wavelength. A laminated wave plate comprising a combination with a material that gives a phase difference. 3. A circularly polarizing plate comprising a laminated body of the laminated wave plate according to claim 2 and a polarizing plate.