JPH04121703A - Phase difference element - Google Patents

Abstract

PURPOSE:To make dependency on wavelengths into arbitrary characteristics by laminating two sheets of phase difference plates which have the dependency on wavelengths and vary in the respective retardation from each other by intersecting the phase advance axes thereof orthogonally with each other and selecting the combinations thereof. CONSTITUTION:The characteristics of the phase difference element are such that the retardation DELTAnd thereof corresponds to the difference (DELTAnd=DELTAn1d1-DELTAn2 d2) between the retardations DELTAn1d1, DELTAn2d2 and the dependency on wavelengths corresponds to the difference in the dependency on wavelengths between two sheets of the phase difference plates 1, 2 when two sheets of the phase difference plates 1, 2 which have the dependency on wavelengths and vary in the respective retardation from each other are laminated by intersecting the phase advance axes A1, A2 thereof orthogonally with each other. The combinations of the phase difference plates 1, 2 are selected by utilizing such characteristics, by which the dependency on wavelengths of the phase difference element is made into the arbitrary characteristics.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a phase difference element.

[Conventional technology]

Retardation elements are used to adjust refractive index anisotropy in optical systems, and conventionally, retardation plates made of diacetate resin plates, acrylic resin plates, etc. have been used alone. ing. In this retardation plate, its refractive index anisotropy Δn is not constant for all wavelengths of light, and therefore, the retardation Δnd (product of refractive index anisotropy Δn and plate thickness d) of this retardation plate is ) has wavelength dependence.

By the way, this retardation plate is used, for example, to compensate for the coloring of transmitted light in a liquid crystal display element (mainly an STN type liquid crystal display element); is the retardation Δ of the retardation plate
It is necessary to set nd to a value corresponding to the retardation Δnd of the liquid crystal display element (the product of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d). In this case, the retardation Δnd of the retardation plate has wavelength dependence, and the retardation Δnd of the liquid crystal display element also has wavelength dependence, so it is necessary to compensate for the coloring of light of all wavelengths in the visible light region. , it is necessary to use a retardation plate that has almost the same wavelength dependence as that of the liquid crystal display element.

[Problem to be solved by the invention]

However, the above-mentioned retardation plate has a unique wavelength dependence determined by its material, manufacturing method, etc., so even if you search for a retardation plate with the desired wavelength dependence among various retardation plates, you will not be able to find the appropriate one. Often there isn't.

For this reason, conventionally, a retardation plate with a wavelength dependence as close as possible to the desired wavelength dependence is selected and used.For example, a retardation plate is used to compensate for colored transmitted light in a liquid crystal display element. In this case, a retardation plate with a wavelength dependence as close as possible to that of the liquid crystal display element is selected and used. Because the color shifts depending on the wavelength of the light, it has not been possible to compensate for the coloration of light of all wavelengths in the visible light region.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a retardation element whose wavelength dependence can be made into an arbitrary characteristic.

[Means to solve the problem]

The retardation element of the present invention is obtained by laminating two retardation plates having wavelength dependence and different retardations at each wavelength, with their fast axes orthogonal to each other.

[Operation] This retardation element is made by laminating two retardation plates with wavelength dependence and different retardations at each wavelength with their fast axes orthogonal to each other. The characteristic of is that the retardation corresponds to the difference in retardation of two retardation plates, and the wavelength dependence corresponds to the difference in wavelength dependence of two retardation plates.
By selecting a combination of retardation plates, the wavelength dependence can be made into an arbitrary characteristic.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of the phase difference element. In the retardation element of this example, the retardation Δnd has wavelength dependence,
It is a stack of two retardation plates 1 and 2 with different retardations at each wavelength, and these two retardation plates 1
, 2 is its fast axis A1. They are stacked with A2's perpendicular to each other.

Note that Bl and B2 are slow axes of each retardation plate 1 and 2,
The slow axes Bl and B2 are also orthogonal to each other.

According to this retardation element, two retardation plates 1.
2 are stacked with their fast axes A, , A2 perpendicular to each other, so the characteristics of this retardation element are that its retardation Δnd is equal to the retardation Δn of the two retardation plates 1 and 2.
, d.

Difference in Δn2 d2 (Δnd-Δn, d, -Δn2d2)
The wavelength dependence corresponds to the difference in the wavelength dependence of the two retardation plates 1°2. Therefore, by selecting a combination of the retardation plates 1 and 2, the wavelength dependence of the retardation element can be made to have arbitrary characteristics.

That is, FIG. 2 shows the characteristics of the two retardation plates 1 and 2, and FIG. 3 shows the characteristics of the retardation element. For example, as shown in FIG. .2, the retardation Δn1dl+ Δn on the long wavelength region side
2 Select a plate with wavelength dependence that increases d2, and use one of the retardation plates 1 as Δn at 40 Or+m.
, d, is 20Or+m700n mark, d, is 50
A plate with a wavelength dependence of 0 nm was used, and as the other retardation plate 1, Δn,d at 400 nm was 100 nm,
When using a retardation element with a wavelength dependence of Δn, d of 300 nm at 700 nm, the characteristics of the retardation element are such that Δn, d at 400 nm is 100 rv, as shown in FIG.

The characteristic is that Δn (dB) at 700 nm has a wavelength dependence of 200 nm.

In addition, in this embodiment, the plate thickness d of one of the retardation plates 1
1 is made thicker than the plate thickness d2 of the other retardation plate 2, the wavelength dependence of the retardation element becomes a characteristic closer to that of one retardation plate 1 than the characteristics shown in FIG. Retardation plate 1
If the thickness d1 of the retardation plate 2 is made thinner than the thickness d2 of the other retardation plate 2, the wavelength dependence of the retardation element will become closer to the characteristics of the other retardation plate 2 than the characteristics shown in FIG. . In this case, if the plate thicknesses dl and d2 of each retardation plate 1 and 2 are appropriately selected,
It is also possible to make the characteristics of the retardation element substantially horizontal, with almost no wavelength dependence.

In addition, in the above embodiment, as the two retardation plates 1.2,
A combination of wavelength-dependent retardation plates with large retardation on the long-wavelength side is used, but this combination of retardation plates 1 and 2 has a wavelength-dependent position with small retardation on the long-wavelength side. It may be a combination of two retardation plates, or a combination of a wavelength-dependent retardation plate that has a large retardation on the long wavelength side and a wavelength-dependent retardation plate that has a small retardation on the long wavelength side. (However, the retardations at each wavelength of both retardation plates 1.2 are different from each other.) In that case, the characteristics of the retardation element are such that the retardation Δnd is the retardation of the two retardation plates 1.2 Δn1dl+ Δn2 d2
The wavelength dependence corresponds to the difference between the two retardation plates 1.2
This characteristic corresponds to the difference in wavelength dependence of .

Note that the retardation element of the present invention can also be used in combination with other retardation plates.

〔Effect of the invention〕

The retardation element of the present invention is made by laminating two retardation plates with wavelength dependence and different retardations at each wavelength, with their fast axes orthogonal, so that the wavelength dependence can be adjusted arbitrarily. can be made into a characteristic.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of the present invention. Figure 1 is a perspective view of a retardation element, Figure 2 is a characteristic diagram of each retardation plate, and Figure 3 is a diagram of the retardation element. It is a characteristic diagram. 1.2... Retardation plate, AI, A2... Fast axis, B1
B2...Slow axis.

Claims (1)

[Claims] A retardation element characterized in that two retardation plates having wavelength dependence and different retardations at each wavelength are laminated with their fast axes orthogonal to each other.