JP2016103013A - Phase difference plate, elliptical polarizing plate, and display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase difference plate that comprises a single-layer film that minimizes a reduction in transmittance and has an abnormal light refractive index ne or birefringence Δn characterized to have "negative dispersion".SOLUTION: There is provided a phase difference plate formed of a film including a polymer obtained by polymerizing a polymerizable liquid crystal composition that has "negative dispersion" characteristics in which birefringence Δn increases as a measurement wavelength becomes longer in at least a part of a wavelength area of a visible light area, and a composition that contains a dichromatic pigment, where the dichromatic pigment is contained in an amount of 0.03 to 0.8 pt.wt. relative to 100 pts.wt. of the polymerizable liquid crystal composition, and the order parameter (S) of the dichromatic pigment in the polymer is within a range of 0.4≤S≤1.0. (1) S=(DR-1)/(DR+2), wherein DR is the absorption dichroic ratio of the dichromatic pigment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a retardation plate used in a liquid crystal display device, an organic electroluminescence display device, and the like, and an image display device such as a liquid crystal display device and an organic electroluminescence display device using the same.

  The retardation plate is an optical element used to obtain polarized light (linearly polarized light, circularly polarized light, elliptically polarized light). Retardation plates are used for color compensation of liquid crystal display devices, viewing angle improvement film applications, antireflection film applications for organic EL display devices that combine polarizing plates and quarter-wave plates, and clockwise or counterclockwise rotation composed of cholesteric liquid crystals, etc. It is used in many applications such as a reflective polarizing plate that reflects only one of the circularly polarized light. As the phase difference plate, a thin plate of inorganic material (calcite, mica, crystal), a stretched film made of a polymer material having a high intrinsic birefringence, a rod-like or disk-like liquid crystal material is aligned and fixed in the liquid crystal state. A film is used.

  As a typical retardation plate, a quarter wavelength plate having a retardation corresponding to ¼ of a wavelength and a ½ wavelength plate having a retardation corresponding to ½ of a wavelength are known. The quarter-wave plate has an optical function of converting linearly polarized light into circularly polarized light. The half-wave plate has a function of converting the polarization vibration plane of linearly polarized light by 90 °.

  The retardation plate is usually designed to give a necessary optical function to light of a specific wavelength (monochromatic light). The quarter-wave plate used in the color compensation film for liquid crystal display devices and the antireflection film for organic EL display devices is circularly polarized linearly polarized light in the visible wavelength region where the measurement wavelength λ is 400 to 700 nm, preferably 400 to 780 nm. In addition, it is necessary to have a function of converting circularly polarized light into linearly polarized light. When this is realized with a single-layer retardation plate, the phase difference may be ¼ wavelength (ie, λ / 4 (nm)) of the measurement wavelength at a measurement wavelength of 400 to 700 nm, preferably 400 to 780 nm. The ideal of the board.

  In general, as the quarter-wave plate, the above-described retardation plate material or the like is used, but these materials have wavelength dispersion (wavelength dependence) in the retardation. Here, the dispersion characteristic in which the phase difference is larger as the measurement wavelength is shorter and the phase difference is smaller as the wavelength is longer is defined as “positive dispersion”. The phase difference is smaller as the wavelength is shorter and the phase difference is longer as the wavelength is longer. The dispersion characteristic that increases is defined as “negative dispersion”. FIG. 1 shows the chromatic dispersion characteristics of birefringence (Δn (λ)) at each wavelength in the visible light region normalized by setting the birefringence value (Δn (550 nm)) at a measurement wavelength of 550 nm to 1. In general, as shown by the solid line in FIG. 1, the birefringence of a polymer film becomes larger as the measurement wavelength becomes shorter and becomes smaller as the longer wavelength. That is, it has “positive dispersion” characteristics. On the other hand, the ideal quarter-wave plate described above has a birefringence proportional to the measurement wavelength as shown by the dotted line in FIG. It has “dispersion” properties. Therefore, it is difficult to obtain an ideal “negative dispersion” characteristic at a measurement wavelength λ = 400 to 700 nm with only one polymer film. When a retardation film made of a general polymer film having such a “positive dispersion” characteristic is applied to white light in which light in the visible light range is mixed, the distribution of the polarization state at each wavelength occurs, and colored The polarized light will be generated.

  JP-A-10-68816 (Patent Document 1) and JP-A-10-90521 (Patent Document 2) disclose a retardation plate in which two polymer films having optical anisotropy are laminated. Yes. The retardation plate described in Patent Document 1 includes a quarter wavelength plate in which the phase difference of birefringent light is a quarter wavelength, and a half wavelength plate in which the phase difference of birefringent light is a half wavelength. Are bonded together with their optical axes intersecting. The retardation plate described in Patent Document 2 is obtained by laminating at least two retardation plates having an optical retardation value of 160 to 320 nm so that their slow axes are not parallel to or orthogonal to each other. It is.

In JP-A-11-52131 (Patent Document 3), the relationship of the wavelength dispersion value α (α = Δn (450 nm) / Δn (650 nm)) of the birefringence index Δn is α _A <α _B 2 A retardation plate in which a plurality of birefringent media are stacked in directions in which respective slow axes are orthogonal to each other, and at least one of the birefringent media is composed of a liquid crystal compound in a molecular orientation state in which the orientation is parallel (homogeneous). _A multilayer retardation plate is disclosed in which the relationship of the phase difference R of each birefringent medium is R _A > R _B and the wavelength dispersion value α is smaller than 1.

  Each of the retardation plates disclosed in Patent Documents 1 to 3 described above is composed of a laminate of two birefringent media. By using such a laminated retardation plate, a wide wavelength region is obtained. Can achieve a quarter-wave plate. However, in order to manufacture the retardation film described in Patent Document 1 and Patent Document 2, a complicated process for adjusting the optical orientation (optical axis and slow axis) of the two polymer films is required. The optical orientation of the polymer film generally corresponds to the longitudinal or lateral direction of the sheet or roll film. Industrial production of a polymer film having an optical axis or a slow axis in an oblique direction of a sheet or roll is difficult. Therefore, in the above-described preparation process of the optical orientation, when adjusting the optical orientation of the two polymer films to an angle that is neither parallel nor orthogonal, it is obtained by cutting two types of polymer films at a predetermined angle. It is necessary to paste the chips together. If the phase difference plate is manufactured by bonding the chips, the processing becomes complicated, the quality is likely to be deteriorated due to axial misalignment, the yield is reduced, and not only the manufacturing cost increases but also deterioration due to contamination is likely to occur. In addition, it is difficult to strictly adjust the optical retardation value in a polymer film.

  By the way, the cause of the birefringence wavelength dispersion of the anisotropic rod-shaped molecule is that the two refractive indexes ne and no of the anisotropic molecule are toward the short wavelength side of the visible wavelength spectrum, as shown in FIG. This is because ne changes more rapidly than no. Here, ne is an “abnormal refractive index” in a direction parallel to the long molecular axis, and no is an “ordinary refractive index” in a direction perpendicular to the long molecular axis. FIG. 3 shows the relationship of the refractive index of the rod-like molecule 1 in the polymer film 2. This is because in the case of an anisotropic rod-like molecule, the functional group having a conjugated double bond is oriented in the major axis direction of the molecule, so the extraordinary ray refractive index ne in the major axis direction is the ultraviolet region close to the visible light region. This is due to the fact that the ordinary ray refractive index no in the short axis direction has a relatively gentle curve.

  One way to achieve higher dispersion of the “positive dispersion” property of birefringence is to design the numerator to increase the positive dispersion of ne and decrease the positive dispersion of no, as shown in FIG. is there. For example, a method of designing a rod-like molecular structure having absorption in the ultraviolet region closer to the visible light region, or mixing a dye having absorption in the ultraviolet region with a polymer can be considered. Japanese Unexamined Patent Publication No. 2000-314885 (Patent Document 4) discloses a retardation plate capable of arbitrarily controlling wavelength dispersion characteristics by mixing an additive that affects the wavelength dispersion characteristics of retardation with a polymer. Has been. The retardation plate described in Patent Document 4 has a short wavelength region compared to the original extraordinary refractive index of the material by adding a dye that absorbs in the ultraviolet region to orient the dye in the long axis direction of the rod-like molecule. It is designed to change more abruptly, and Patent Document 4 clearly states that the “positive dispersion” property of the phase difference can be further increased. However, as a method for imparting a “negative dispersion” characteristic, only a method of superimposing two polymer films added with a dye perpendicularly is disclosed.

  On the other hand, as a method of obtaining “negative dispersion” characteristics in which the birefringence increases as the wavelength increases, the molecule is designed to increase the positive dispersion of no and decrease the positive dispersion of ne as a tendency opposite to FIG. Although it is conceivable that no such material has been found at present.

  As another method for obtaining a “negative dispersion” characteristic in which the birefringence becomes larger as the wavelength increases, it is a prior art to mix a compound composed of a positive birefringent material and a negative birefringent material having different birefringence wavelength dispersion characteristics. Has been proposed in By this method, a retardation plate having “negative dispersion” characteristics can be obtained with a single film.

  For example, Japanese Patent Laid-Open No. 2002-48919 (Patent Document 5) discloses a mixture of at least two kinds of organic polymers composed of an organic polymer having positive birefringence and an organic polymer having negative birefringence, or It is disclosed that a retardation film having “negative dispersion” characteristics can be realized with a single film by forming a retardation film obtained by uniaxially stretching a copolymer film. The retardation film described in Patent Document 5 will be described with reference to the schematic diagram shown in FIG. 5 and the birefringence wavelength dispersion graph shown in FIG. If the extraordinary ray refractive index ne1 and the ordinary ray refractive index no1 of the organic polymer having “positive birefringence” (rod-like molecule 1 in FIG. 5), birefringence Δn1 (= ne1−no1)> 0. When an extraordinary ray refractive index ne2 and an ordinary ray refractive index no2 of an organic polymer having “negative birefringence” (the discotic molecule 3 in FIG. 5), Δn2 (= ne2−no2) <0. Here, in the case of combining materials in which the birefringence Δn1 of the organic polymer having “positive birefringence” is larger than the birefringence Δn2 of the organic polymer having “negative birefringence” (that is, Δn1> Δn2) Case), the total birefringence Δn = Δn1 + Δn2> 0, and the mixture is “positive birefringence”.

  Further, the chromatic dispersion characteristic D1 of the birefringence Δn1 of the organic polymer having “positive birefringence” is expressed as D1 = Δn1 (450) / Δn1 (650) (where Δn1 (450) and Δn1 (650) are The birefringence of the polymer film at the measurement wavelengths of 450 nm and 650 nm, respectively.), And the wavelength dispersion characteristic D2 of the birefringence Δn2 of the organic polymer having “negative birefringence”, D2 = Δn2 (450) / Δn2 ( 650) (where Δn2 (450) and Δn2 (650) are the birefringence of the polymer film at the measurement wavelengths of 450 nm and 650 nm, respectively), as shown in FIG. The wavelength dispersion characteristic D2 of the organic polymer having “birefringence” is larger than the wavelength dispersion characteristic D1 of the organic polymer having “positive birefringence” (that is, D2 Designing D1) so, as the mixture, a phase difference plate having a "positive birefringence" and "negative dispersion" characteristics.

  However, a retardation film formed by uniaxially stretching a copolymer film has a very small birefringence Δn. Therefore, it is necessary to increase the thickness to 50 to 200 μm in order to provide quarter-wave plate characteristics. There is. In recent years, a retardation layer used for a liquid crystal display device or an organic EL display device is required to be thinned, and a polymer stretched film having a small birefringence Δn is desired to be improved from the viewpoint of film thickness.

  Japanese Patent Application Laid-Open No. 2002-267838 (Patent Document 6) discloses a liquid crystal film made of a rod-like liquid crystal compound as a retardation film that is a thin film and has a measurement wavelength that increases as the wavelength increases. The retardation plate described in Patent Document 6 aligns a liquid crystal compound containing a compound having two or more kinds of mesogenic groups and a rod-like liquid crystal molecule in parallel, and at least one kind of mesogen group is in the optical axis direction of the rod-like liquid crystal compound. , Making use of orientation in a substantially orthogonal direction. The rod-like liquid crystal compound has a relatively large birefringence Δn compared to the copolymer resin, and therefore has a thickness of several μm, which is advantageous in terms of thinning the retardation plate.

  However, with the methods proposed in Patent Document 5 and Patent Document 6, it is possible to obtain a characteristic that the phase difference becomes a quarter wavelength of the measurement wavelength in a wide-band region of the measurement wavelength of 400 to 700 nm that is the visible light region. In general, as shown in FIG. 7, in particular, the long wavelength side tends to deviate from the ideal straight line. This is because, as can be seen from the birefringence wavelength dispersion curve shown in FIG. 1, the slopes of the curve on the shorter wavelength side and the curve on the longer wavelength side than the center wavelength of visible light 550 nm are different. Therefore, in order to obtain an ideal chromatic dispersion characteristic in a wide-band region of a measurement wavelength of 400 to 700 nm that is a visible light region, a long wavelength can be obtained by another method while maintaining the short wavelength side curve close to an ideal straight line. An attempt to bring the wavelength curve closer to the ideal straight line is necessary.

  Incidentally, in Japanese Patent Laid-Open No. 6-16955 (Patent Document 7), Japanese Patent Laid-Open No. 2009-9062 (Patent Document 8), Japanese Patent Laid-Open No. 2010-1368 (Patent Document 9), etc., there are “negative dispersion” characteristics. It is disclosed that a dye such as anthraquinone is added to a liquid crystal molecule that does not have a liquid crystal. However, an example in which a dichroic dye is added to liquid crystal molecules having the “negative dispersion” characteristics as described above has not been disclosed yet.

  Japanese Patent Laid-Open No. 2011-178946 (Patent Document 10) discloses that a dichroic dye is added as a dye to be added to a phase difference plate made of a liquid crystal compound. An example of adding a dichroic dye to a liquid crystal molecule having the “dispersion” characteristic has not yet been disclosed. Further, JP 2013-33249 A (Patent Document 11) discloses a polarizing element in which a dichroic dye is added to a smectic liquid crystal compound.

JP-A-10-68816 JP-A-10-90521 Japanese Patent Laid-Open No. 11-52131 JP 2000-314885 A JP 2002-48919 A JP 2002-267838 A Japanese Patent Laid-Open No. 6-16955 JP 2009-9062 A JP 2010-1368 A JP 2011-178946 A JP 2013-33249 A

  The inventors of the present invention have mixed the organic polymer with at least one dichroic dye so that the extraordinary ray refractive index ne becomes longer as the measurement wavelength becomes longer in at least a part of the wavelength region of the visible light region. We found that we can realize a new phase difference plate with large “negative dispersion” characteristics, and optimized the birefringence wavelength dispersion characteristics of liquid crystal compounds, the absorption maximum wavelength of dichroic dyes, and the mixing amount, as well as the film formation conditions. By optimizing the above, it is proposed that a new retardation plate having a “negative dispersion” characteristic in which the birefringence Δn becomes larger as the measurement wavelength becomes longer in at least a part of the wavelength region of the visible light region can be realized. doing.

  In the present invention, when a polymer having a negative dispersion characteristic is used as an organic polymer, if the dichroic dye to be added has a predetermined molecular length, the present invention has two molecules in the alignment direction of the polymer. It has been found that the chromatic dye can be easily oriented and the dichroic ratio can be greatly improved. If a dichroic dye as described above is used, a high dichroic ratio can be obtained while suppressing the amount of dichroic dye added, even when a polymer having negative dispersion characteristics is used. Therefore, as a result, it has been found that it is possible to realize a retardation film composed of a single layer film in which an extraordinary ray refractive index ne or birefringence Δn has a “negative dispersion” characteristic while maintaining a high transmittance. It was. The present invention is based on this finding.

  Accordingly, an object of the present invention is to provide a retardation plate composed of a single layer film in which an extraordinary ray refractive index ne or birefringence Δn has a “negative dispersion” characteristic while minimizing a decrease in transmittance. It is.

  Another object of the present invention is to provide an elliptically polarizing plate having the retardation plate, a liquid crystal display device having the elliptically polarizing plate, and an image display device such as an organic electroluminescence display device.

The retardation plate according to the present invention comprises a polymerizable liquid crystal composition having a “negative dispersion” characteristic in which birefringence Δn is increased as the measurement wavelength is longer in at least part of the wavelength region of the visible light region, and dichroism. A retardation plate comprising a film comprising a polymer obtained by polymerizing a composition containing a dye,
Containing 0.03 to 0.8 parts by weight of the dichroic dye with respect to 100 parts by weight of the polymerizable liquid crystal composition;
The order parameter (S) of the dichroic dye in the polymer represented by the following formula (1) is in the range of 0.4 ≦ S ≦ 1.0.
S = (DR-1) / (DR + 2) (1)
(In the formula (1), DR is an absorption dichroic ratio of the dichroic dye represented by the following formula (2).)
(In the formula (2), λ represents the wavelength (nm) of light in vacuum,
A _e (λ) represents a polarization absorption spectrum parallel to the slow axis in the polymer,
A _o (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the polymer,
A _e0 (λ) represents a polarization absorption spectrum parallel to the slow axis in a polymer obtained by polymerizing only the polymerizable liquid crystal composition excluding the dichroic dye,
A _o0 (λ) represents a polarized light absorption spectrum perpendicular to the slow axis in a polymer obtained by polymerizing only the polymerizable liquid crystal composition excluding the dichroic dye. ).

  In the retardation plate according to the present invention, the extraordinary ray refractive index ne or birefringence Δn has a “negative dispersion” characteristic that increases as the measurement wavelength increases in at least a part of the wavelength region of the visible light region. Good.

  In the retardation plate according to the present invention, the orientation of the polymer may be in a parallel orientation state.

  In the retardation plate according to the present invention, the dichroic dye may be a rod-like molecule, and the molecular length in the major axis direction may be 2 nm to 10 nm.

  In the retardation plate according to the present invention, the absorption maximum wavelength of the dichroic dye may be in a range of a measurement wavelength of 400 to 780 nm.

  In the retardation plate according to the present invention, the absorption maximum wavelength of the dichroic dye may be different from the absorption maximum wavelength of the emission spectrum of the image display device.

  Moreover, as another aspect of the present invention, an elliptically polarizing plate including a retardation plate and a polarizing plate, and an image display device including the elliptically polarizing plate are also provided.

  The image display device according to another aspect of the present invention may be a liquid crystal display device or an organic electroluminescence display device.

  According to the present invention, when the dichroic dye satisfying the above formula (1) is a polymer, the birefringence Δn has a long measurement wavelength in at least a part of the wavelength region of the visible light region. By adding to a polymerizable liquid crystal composition having a “negative dispersion” characteristic that increases as much as possible, the extraordinary ray refractive index ne or birefringence Δn has a “negative dispersion” characteristic while minimizing the decrease in transmittance. A retardation film composed of a single layer film can be realized.

  Further, according to the present invention, the retardation plate having the birefringence wavelength dispersion as described above and having a phase difference of ¼ wavelength at a measurement wavelength of 550 nm can convert circularly polarized light into linearly polarized light in a wide wavelength region. Because it functions as a phase difference plate that converts linearly polarized light into circularly polarized light, its brightness, contrast ratio, etc. are improved when used in liquid crystal display devices, and high anti-specular performance when used in organic electroluminescence display devices. Greatly improves the contrast.

It is a figure which shows the comparison with the wavelength dispersion of a general polymer film and ideal birefringence (DELTA) n. It is a figure which shows the comparison with the wavelength dispersion of the extraordinary ray refractive index ne and the ordinary ray refractive index no of the rod-shaped molecule | numerator which has anisotropy. It is a figure which shows the polymer film 2 which consists of the organic polymer (rod-shaped molecule) 1 which has positive birefringence. It is a figure which shows the comparison with the wavelength dispersion of the extraordinary ray refractive index ne of a rod-shaped molecule | numerator, and the ordinary ray refractive index no for demonstrating the method of making higher the "positive dispersion | distribution" characteristic of birefringence. It is a figure which shows the polymer film 2 which consists of the organic polymer (rod-shaped molecule) 1 which has positive birefringence, and the organic polymer (disk-shaped molecule) 3 which has negative birefringence. It is a figure explaining that birefringence expresses a "negative dispersion" characteristic by the polymer film which consists of an organic polymer which has positive birefringence, and an organic polymer which has negative birefringence. It is a figure which shows the comparison with the phase difference plate which has a "negative dispersion | distribution" characteristic, and ideal birefringence wavelength dispersion. It is a figure which shows the wavelength dispersion characteristic of the refractive index and absorption coefficient of an organic molecule. It is the figure which expanded the anomalous dispersion | distribution area | region of FIG. It is a figure which shows the comparison with the wavelength dispersion of the extraordinary ray refractive index ne and the ordinary ray refractive index no before and after adding a dichroic dye to the organic polymer which has anisotropy. It is a figure which shows the comparison with the absorption spectrum of the long-axis direction (ne direction) and short-axis direction (no direction) of the dye molecule of a dichroic dye. It is a figure which shows the comparison with the wavelength dispersion of birefringence (DELTA) n before and after adding a dichroic dye to the organic polymer which has anisotropy. It is a figure of the emission spectrum when the organic electroluminescence display device of Example 2 and Comparative Example 1 emits white and displays three emission colors of red, blue, and green at the same time. It is a figure which shows the wavelength dispersion characteristic of birefringence (DELTA) n of the liquid crystal film produced in Example 2. FIG.

  When the retardation plate according to the present invention is a polymer, a polymerizable liquid crystal having a “negative dispersion” characteristic in which the birefringence Δn becomes larger as the measurement wavelength is longer in at least a part of the wavelength region of the visible light region. It comprises a film comprising a polymer obtained by polymerizing a composition containing the composition and at least one dichroic dye. Before describing the retardation plate of the present invention, the difference between the conventional retardation plate and the retardation plate of the present invention will be described.

[Comparison with conventional retardation plate]
First, the refractive index wavelength dispersion characteristic of the organic polymer will be described with reference to FIG.
In the following, the refractive index is the complex number N = n−ik, where n is the real part of N and is usually equal to what is called “refractive index.” K (the imaginary part of N) is a function of wavelength α ( It is expressed as k = αλ / (4π) as λ) and related to the absorption coefficient.

  In general, in an organic polymer, the refractive index n in a region away from the intrinsic absorption wavelength (regions a1, a2, and a3 in FIG. 8) monotonously decreases as the wavelength increases. Such dispersion is called “normal dispersion”, and k = 0 in this dispersion region. On the other hand, the refractive index n in the wavelength region including intrinsic absorption (regions b1, b2, and b3 in FIG. 8) increases rapidly as the wavelength increases. Such dispersion is called “anomalous dispersion”. In the present specification, “normal dispersion” is expressed as “positive dispersion” and “abnormal dispersion” is expressed as “negative dispersion”.

  Since the conventional phase difference plate has no absorption in the visible light region, the curves of the extraordinary ray refractive index ne and the ordinary ray refractive index no both have a “positive dispersion” characteristic in the visible light region. Therefore, the prior art proposed as a method for obtaining the “negative dispersion” characteristic in which the birefringence increases as the wavelength increases, and the organic polymer having the “positive birefringence” and the organic high-power having the “negative birefringence”. The copolymer or mixture of molecules has an extraordinary ray refractive index ne and an ordinary ray refractive index no both having a “positive dispersion” characteristic.

  On the other hand, in the present invention, by adding a dichroic dye having absorption in the visible light region to an organic polymer having a refractive index “positive dispersion” characteristic, at least a part of the wavelength in the visible light region is added. In the region, the design philosophy is fundamentally different from the prior art in that the extraordinary ray refractive index ne becomes a phase difference plate having “negative dispersion” characteristics than before the addition of the dichroic dye.

[Phase difference plate of the present invention]
The retardation plate according to the present invention is a retardation plate made of a film containing an organic polymer and at least one dichroic dye, and has retardation characteristics satisfying the above formula (1). It is a new phase difference plate. In the present invention, the retardation ratio at a predetermined wavelength of a retardation plate made of a film containing a dichroic dye is more than the retardation ratio at a predetermined wavelength of a retardation plate made of a film not containing a dichroic dye. By increasing the size, it is possible to realize a retardation plate having an extraordinary ray refractive index ne or birefringence Δn having a “negative dispersion” characteristic, even if the retardation plate is made of a single layer film. When the retardation plate does not satisfy the above formula (1), the birefringence wavelength dispersibility characteristics are insufficient, and the display characteristics (contrast and color) when mounted on a liquid crystal display device or when mounted on an organic EL display device There is a possibility that troubles occur, such as a decrease in the antireflection performance of the.

  The retardation plate according to the present invention is a retardation plate in which the extraordinary ray refractive index ne or the birefringence index Δn has a “negative dispersion” characteristic in at least a part of the wavelength region of the visible light region. A design method of the extraordinary ray refractive index ne or the birefringence index Δn having the “negative dispersion” characteristic that is the characteristic of the retardation plate according to the present invention will be described.

  A mixture or copolymer film of at least two kinds of organic polymers composed of an organic polymer having positive birefringence and an organic polymer having negative birefringence exemplified in Patent Document 5 above is uniaxially stretched. 7 or a liquid crystal film comprising a liquid crystal compound containing a compound having two or more kinds of mesogenic groups and rod-like liquid crystal molecules exemplified in Patent Document 6 above, “positive birefringence” and “negative” as shown in FIG. The phase difference plate has a “dispersion” characteristic. However, in general, as shown in FIG. 7, the long wavelength side deviates from the ideal straight line due to the difference in the slope of the curve on the shorter wavelength side and the longer wavelength side than the central wavelength of visible light 550 nm. There is a tendency. Therefore, in order to approach the ideal chromatic dispersion characteristics in the wide-band region of the measurement wavelength 400 to 700 nm, which is the visible light region, the curve on the short wavelength side is maintained in a state close to the ideal straight line, while another method is used. An attempt to bring the wavelength curve closer to the ideal straight line is necessary. In the present invention, in view of the above situation, attention was paid to the “negative dispersion” characteristic caused by the anomalous dispersion region of the organic polymer.

  FIG. 9 shows an enlarged view of the “abnormal dispersion region” curve in FIG. Assuming a symmetric absorption band, the contribution of anomalous dispersion is approximately zero at the maximum absorption value in the “abnormal dispersion region”, and the local maximum value of the refractive index is the absorption wavelength of the long wavelength side. It appears just before the half-wave peak value, and the local minimum value of the refractive index appears just after the half-wave peak value on the short wavelength side. These positions are shown in FIG. 9 as λmax, λ +, and λ−. That is, there is a so-called “negative dispersion” characteristic in which the refractive index increases as the wavelength increases from λ− to λ +.

Next, the design concept of the present invention will be described with reference to FIGS.
As shown by the thin lines in FIG. 10 (the solid line is ne and the dotted line is no), in general, in the case of an organic polymer having anisotropy, the type of dipole differs depending on the axial direction. The rate no indicates a different “positive dispersion” curve. When a dye having high dichroism having an absorption spectrum having an absorption maximum wavelength at 580 nm as shown in FIG. 11 is added to this organic polymer, extraordinary ray refraction occurs in the wavelength region of 550 to 650 nm, which is near the absorption wavelength. A retardation plate having a characteristic that the ratio ne has “negative dispersion” is obtained. Here, high dichroism means that the difference in absorption characteristics of the dichroic dye is large between the ne direction and the no direction of the organic polymer. FIG. 12 shows the birefringence wavelength dispersion characteristics of the retardation plate made of an organic polymer before and after the addition of the dichroic dye. It can be seen that by adding a dichroic dye, a phase difference plate having birefringence having “negative dispersion” can be obtained in a wavelength region of 550 to 650 nm.
From the above, by adding a dichroic dye having an anomalous dispersion region to an organic polymer having anisotropy, birefringence is closer to ideal in the entire wavelength region of visible light, which is also the object of the present invention. A retardation plate having “negative dispersion” characteristics is obtained.

  FIG. 12 shows data obtained by adding a dichroic dye to an organic polymer whose birefringence has a “positive dispersion” characteristic. By adding a dichroic dye to a retardation plate having a “negative dispersion” characteristic of birefringence as described in Patent Document 5 and Patent Document 6 above, “negative dispersion in a wide visible light region” It is possible to obtain a phase difference plate having the characteristics.

  For example, the retardation plate having the “negative dispersion” characteristic shown in FIG. 7 has a relatively close-to-ideal state on the shorter wavelength side than the visible light center wavelength of 550 nm, but on the longer wavelength side than 550 nm. Tend to deviate significantly from ideals. By adding and orienting a high dichroic dye having an absorption maximum in the visible light region to such a phase difference plate, the chromatic dispersion characteristic on the short wavelength side is maintained, and an ideal straight line is also formed on the long wavelength side. It is possible to have close dispersion characteristics.

  In the above-described Patent Document 4, dyes that absorb in the ultraviolet region, dyes that absorb in the infrared region, and pigments that absorb in the visible region are listed as examples. Although there is an explanation about the design according to, there is no mention in Patent Document 4 regarding the design concept of the present invention of designing an extraordinary ray refractive index ne having a “negative dispersion” characteristic. In addition, the addition of a pigment material causes the retardation plate to be colored, which is a problem as a retardation plate material that is required to be transparent with visible light. However, Patent Document 4 avoids these problems. No method is mentioned.

  The retardation plate according to the present invention has a “negative dispersion” characteristic in which the extraordinary ray refractive index ne or birefringence Δn becomes larger as the measurement wavelength is longer in at least a part of the wavelength region of the visible light region. Here, the visible light region generally represents a wavelength region of 400 nm to 780 nm, but as a region where the refractive index ne exhibits “negative dispersion” characteristics, a region including a visible light center wavelength of around 550 nm is preferable. This is because the sensitivity of brightness perceived by human eyes for each wavelength (hereinafter referred to as specific visual sensitivity) is maximum near 555 nm, and maximum near 507 nm in dark places.

  Originally, the extraordinary ray refractive index ne is preferably larger as the wavelength is longer over the entire visible light wavelength. However, as described later, it is necessary to increase the addition amount of the dye material, which is not preferable in terms of coloring of the retardation plate. In addition, in consideration of human specific visual sensitivity characteristics, if a "negative dispersion" characteristic can be obtained within a wavelength range of 550 to 650 nm, preferably within a wavelength range of 550 to 600 nm, sufficiently desired characteristics can be obtained. It is.

The retardation plate according to the present invention is characterized in that the birefringence Δn has a “negative dispersion” characteristic that increases as the measurement wavelength increases in at least a part of the wavelength region of the visible light region. More specifically, retardations (product of birefringence Δn and retardation film thickness d) at wavelengths of 450 nm, 550 nm, and 650 nm are respectively expressed as Δn · d (450) and Δn · d (550). , Δn · d (650), it is preferable that the following expressions (3) and (4) are satisfied.
0.70 <Δn · d (450) / Δn · d (550) <1.00 (3)
1.00 <Δn · d (650) / Δn · d (550) <1.30 (4)
More preferably, the following formulas (3-1) and (4-1) are satisfied.
0.80 <Δn · d (450) / Δn · d (550) <0.95 (3-1)
1.02 <Δn · d (650) / Δn · d (550) <1.20 (4-1)

Further, in consideration of specific visibility characteristics, retardation of retardation plate (product of birefringence Δn and retardation plate thickness d) at wavelengths of 500 nm, 550 nm, and 580 nm at a more preferable measurement wavelength of 550 nm to 580 nm, When Δn · d (500), Δn · d (550), and Δn · d (580) are satisfied, it is preferable that the following expressions (5) and (6) are satisfied.
0.80 <Δn · d (500) / Δn · d (550) <1.10 (5)
1.00 <Δn · d (580) / Δn · d (550) <1.15 (6)
More preferably, the following formulas (4-1) and (5-1) are satisfied.
0.85 <Δn · d (500) / Δn · d (550) <1.05 (5-1)
1.02 <Δn · d (580) / Δn · d (550) <1.12 (6-1)

  When the retardation of the retardation plate is out of the above range, for example, when used as a quarter-wave plate, polarized light obtained when 400-700 nm linearly polarized light is incident on this film (retardation plate). The state can be completely circularly polarized at a specific wavelength, but may be greatly deviated from circularly polarized light at other wavelengths.

  The phase difference plate may be required to have a specific phase difference value as well as a film thickness depending on its application. Here, the retardation value (Δn · d) of the retardation film is preferably 20 nm to 450 nm (more preferably 50 nm to 300 nm). In this specification, “retardation value (Δn · d)” is a retardation value for light having a wavelength of 550 nm. The retardation value can be measured by a conventionally known method. For example, a device capable of measuring birefringence (for example, a trade name “Axoscan” manufactured by Axometrix, a trade name “KOBRA” manufactured by Oji Scientific Instruments). -21ADH "etc.).

  The retardation plate according to the present invention has the optical characteristics as described above. In order to realize such optical characteristics, the birefringence Δn when the polymer is used is at least part of the visible light region. In the wavelength region, a film is formed by forming a polymer obtained by polymerizing a composition in which a specific dichroic dye is added to a polymerizable liquid crystal composition having a “negative dispersion” characteristic that increases as the measurement wavelength increases. A phase difference plate is used. Hereinafter, the polymerizable liquid crystal composition and the dichroic dye used in the retardation plate according to the present invention will be described.

[Polymerizable liquid crystal composition]
The polymerizable liquid crystal composition used in the present invention will be described. The polymerizable liquid crystal composition is not particularly limited as long as it contains a liquid crystal compound capable of fixing the alignment state by polymerization. The polymerizable liquid crystal composition in the present invention includes a liquid crystal compound having one or more polymerizable groups (polymerizable liquid crystal compound), a liquid crystal compound having no polymerizable group, and a polymerizable compound not exhibiting liquid crystallinity. A mixture of a liquid crystal compound having a polymerizable group and a polymerizable compound not exhibiting liquid crystallinity, and a mixture of a liquid crystal compound having a polymerizable group and a liquid crystal compound having no polymerizable group. There may be.

  Moreover, as such a polymerizable liquid crystal composition, a polymerizable liquid crystal compound having a polymerizable group that reacts with light and / or heat is preferable from the viewpoint that the alignment state can be more efficiently fixed. Such a liquid crystal compound having a polymerizable group that reacts with light or heat can be polymerized with a component (liquid crystal compound or the like) present around it by light and / or heat to fix the alignment. The type is not particularly limited, and a liquid crystal compound having a known polymerizable group can be appropriately used. Such a polymerizable group is preferably a vinyl group, a (meth) acryloyl group, a vinyloxy group, an oxiranyl group, an oxetanyl group, an aziridinyl group, or the like. As such a polymerizable group, other polymerizable groups such as an isocyanate group, a hydroxyl group, an amino group, an acid anhydride group, and a carboxyl group may be used depending on the reaction conditions.

  Furthermore, as such a polymerizable liquid crystal compound, a liquid crystal compound having a (meth) acryloyl group as a polymerizable group is preferable from the viewpoint of availability, heat resistance, and handleability, and a (meth) acrylate liquid crystal compound ( It is more preferable to use (a liquid crystal compound having a (meth) acrylate group). In the present invention, “methacryloyl” and “acryloyl” are sometimes collectively referred to as “(meth) acryloyl”, and “methacrylate” and “acrylate” are sometimes collectively referred to as “( “Meth) acrylate”, and in some cases, “methacryl” and “acryl” are collectively referred to as “(meth) acryl”. Further, the “(meth) acrylate group” refers to a residue ((meth) acryloyloxy group) in which hydrogen is eliminated from the carboxyl group of (meth) acrylic acid.

As such a (meth) acrylate type liquid crystal compound, compounds represented by the following general formulas (10) to (12) are preferable.

In the general formulas (10) to (12), each W independently represents one of H and CH ₃ . Depending on the kind of W, in the formula, a group represented by CH ₂ = CWCOO is either an acrylate group or a methacrylate group. N is an integer of 1 to 20 (more preferably 2 to 12, more preferably 3 to 6). If such a value of n is within the above numerical range, the temperature range in which the compound exhibits liquid crystallinity is widened, and the fluidity derived from the liquid crystal of the compound necessary for realizing good parallel alignment is obtained. As a result, good parallel orientation can be realized.

In the general formula (10), R ^a represents any group selected from an alkyl group having 1 to 20 carbon atoms and an alkoxy group having 1 to 20 carbon atoms. Such an alkyl group having 1 to 20 carbon atoms that can be selected as ^Ra is preferably one having 1 to 12 carbon atoms, and more preferably 3 to 6 carbon atoms. If such a carbon number is within the above numerical range, as a result of maintaining the fluidity derived from the liquid crystal of the compound necessary for realizing a good parallel orientation, a good parallel orientation can be realized, In addition, the temperature range in which the compound exhibits liquid crystallinity is widened. Such an alkyl group may be linear, branched, or cyclic, and is not particularly limited. Is more preferably linear.

Moreover, as for the C1-C20 alkoxy group which can be selected as Ra, ^a C1-C12 thing is more preferable, and a C3-C6 thing is still more preferable. If such a carbon number is within the above numerical range, as a result of maintaining the fluidity derived from the liquid crystal of the compound necessary for realizing a good parallel orientation, a good parallel orientation can be realized, In addition, the temperature range in which the compound exhibits liquid crystallinity is widened. The alkoxy group has a structure in which an alkyl group is bonded to an oxygen atom. The structure of the alkyl group portion may be linear, branched, or cyclic. Although not particularly limited, a straight-chain one is more preferable from the viewpoint of realizing a good parallel orientation.

In the general formula (12), Z ¹ and Z ² each independently represent any group of —COO— and OCO—. As such Z ¹ and Z ² , one group of Z ¹ and Z ² is a group represented by —COO—, and the other group is — A group represented by OCO- is preferable.

In the general formula (12), X ¹ and X ² each independently represent any of H and an alkyl group having 1 to 7 carbon atoms. The alkyl group having 1 to 7 carbon atoms that can be selected as X ¹ and X ² is more preferably 1 to 3 carbon atoms (the alkyl group is CH ₃ ). Is more preferable. When the number of carbon atoms is within the above numerical range, a good parallel orientation can be realized. Thus, it is particularly preferable that the X ¹ and X ² are each independently one of H and CH ₃ .

  Examples of the (meth) acrylate liquid crystal compounds represented by the general formulas (10) to (12) include compounds described in the following general formulas (110) to (113). Such (meth) acrylate liquid crystal compounds may be used singly or in combination of two or more.

  The polymerizable liquid crystal compound is preferably used in combination with the compounds represented by the general formulas (10) to (12), and is combined with the compounds represented by the general formulas (110) to (113). It is more preferable to use it.

  As described above, when the compounds represented by the general formulas (10) to (12) are used in combination as the polymerizable liquid crystal compound, the content of the compound represented by the general formula (10) It is preferably 20 to 60% by weight, more preferably 30 to 45% by weight, based on the total amount of the compounds represented by formulas (10) to (12). If the content of the compound represented by the general formula (10) is within the above numerical range, an orientation defect tends to occur with respect to the parallel orientation. It is possible to suppress the occurrence of defects.

  In the case where the compounds represented by the general formulas (10) to (12) are used in combination, the content of the compound represented by the general formula (11) is represented by the general formulas (10) to (12). It is preferable that it is 10 to 50 weight% with respect to the total amount of the compound represented, and it is more preferable that it is 20 to 30 weight%. If the content of the compound represented by the general formula (11) is within the above numerical range, it is possible to suppress the occurrence of alignment defects with respect to parallel alignment.

  Further, when the compounds represented by the general formulas (10) to (12) are used in combination, the content of the compound represented by the general formula (12) is represented by the general formulas (10) to (12). It is preferably 10 to 70% by weight, more preferably 25 to 45% by weight, based on the total amount of the compound represented. If content of such a compound represented by General formula (12) is in the said range, it can suppress that an orientation defect arises regarding parallel orientation.

  Furthermore, in the case where the compounds represented by the general formulas (110) to (113) are used in combination as the polymerizable liquid crystal compound, the mass ratio of each compound is ([above Compound Represented by General Formula (110)]: [Compound Represented by General Formula (111)]: [Compound Represented by General Formula (112)]: [Compound Represented by General Formula (113)]) Is preferably 45: 40: 15: 0 to 35: 5: 30: 30, and more preferably 35: 23: 23: 19 to 38: 25: 25: 12.

  Moreover, the manufacturing method in particular of a polymeric liquid crystal compound is not restrict | limited, A well-known method can be utilized suitably. For example, when the compound represented by the above general formula (110) is produced, for example, the method described in British Patent Application Publication No. 2,280,445 may be adopted, and the above general formula ( 111) is produced, for example, D.I. J. et al. The method described in pages 3201 to 3215 of “Macromol. Chem. (Vol. 190, published in 1989)” by Broer et al. May be employed, and is represented by the above general formulas (112) to (113). For example, a method described in International Publication WO 93/22397 may be employed. Thus, the polymerizable liquid crystal compound can be produced by appropriately using a known method according to the type of the compound to be used. Moreover, you may utilize a commercial item as such a polymeric liquid crystal compound. Further, such polymerizable liquid crystal compounds may be used alone or in combination of two or more.

In the retardation plate according to the present invention, the retardation Δn · d (product of birefringence Δn and the thickness d of the retardation plate) preferably satisfies the following expressions (3) and (4).
0.70 <Δn · d (450) / Δn · d (550) <1.00 (3)
1.00 <Δn · d (650) / Δn · d (550) <1.30 (4)
Further, in consideration of the relative visibility characteristic, the retardation plate according to the present invention has a retardation Δn · d (product of birefringence Δn and the thickness d of the retardation plate) at a more preferable measurement wavelength of 550 nm to 580 nm. It is preferable that the following formulas (5) and (6) are satisfied.
0.80 <Δn · d (500) / Δn · d (550) <1.10 (5)
1.00 <Δn · d (580) / Δn · d (550) <1.15 (6)
In particular, as a method of satisfying the requirement of the formula (1), the polymerizable polymer compound is a compound having two or more kinds of mesogenic groups, and at least one of the mesogenic groups is arranged with respect to the slow axis of the parallel alignment of the liquid crystal layer. Japanese Patent Application Laid-Open No. 2002-267838 and Japanese Patent Application Laid-Open No. 2010-31223 indicate that the phase difference increases as the wavelength becomes longer by orienting in the substantially orthogonal direction. Here, the mesogen of the mesogen group is also an intermediate phase (= liquid crystal phase) forming molecule ("Liquid Crystal Dictionary", Japan Society for the Promotion of Science, 142nd Committee on Organic Materials for Information Science, edited by Liquid Crystal Division, 1989) And is almost synonymous with the liquid crystalline molecular structure. In the present invention, it is preferable to employ a mesogenic group in the rod-like liquid crystal (molecular structure relating to liquid crystallinity of the rod-like liquid crystal). The mesogenic group in the rod-like liquid crystal is described in various documents (for example, Flussige Kristalle in Tabellen, VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig (1984), Volume 2).

  Examples of mesogenic groups include biphenyl, phenylcyclohexyl, cyclohexylphenyl, phenyloxycarbonylphenyl, phenylcarbonyloxyphenyl, phenyloxycarbonylcyclohexyl, cyclohexylcarbonyloxyphenyl, phenylcarbonyloxyphenyloxycarbonylphenyl, phenylcarbonyloxyphenyloxycarbonylphenyl , Phenylcarbonyloxycyclohexyloxycarbonylphenyl, phenyloxycarbonylcyclohexylcarbonyloxyphenyl, phenylcarbonyloxyphenylaminocarbonylphenyl, phenylethenylenephenyl, phenylethynylenephenyl, phenylethynylenephenylethynylenephenyl, phenylethenylenecarbonyloxy Include phenyl and phenyl et tennis alkyleneoxy phenyl ethynylenes phenyl.

  The mesogenic group (a benzene ring or a cyclohexane ring constituting the mesogenic group) may have a substituent. As the substituent, the polymerizable group described above or a derivative thereof is preferable. As a combination of two kinds of mesogenic groups, one mesogenic group is biphenyl, phenylcyclohexyl, cyclohexylphenyl, phenyloxycarbonylphenyl, phenylcarbonyloxyphenyl, phenyloxycarbonylcyclohexyl, cyclohexylcarbonyloxyphenyl, phenylcarbonyloxyphenyloxycarbonyl. Selected from the group consisting of phenyl, phenylcarbonyloxyphenyloxycarbonylphenyl, phenylcarbonyloxycyclohexyloxycarbonylphenyl, phenyloxycarbonylcyclohexylcarbonyloxyphenyl and phenylcarbonyloxyphenylaminocarbonylphenyl, the other mesogenic group is phenylethenylenephenyl Phenylethynylenepheny , Phenyl ethynylene phenyl ethynylene phenyl, particularly preferably selected from the group consisting of phenyl et tennis alkylene carbonyloxy biphenyl and phenyl et tennis alkyleneoxy phenyl ethynylenes phenyl.

  A compound having two or more kinds of mesogenic groups can be synthesized by applying a general synthesis method. For example, 1) a sequential introduction method in which one of two or more kinds of mesogenic groups is first introduced by functional group conversion of the starting material, and then another mesogenic group is continuously introduced by functional group conversion; 2) starting material It is possible to adopt a simultaneous introduction method in which two or more kinds of mesogenic groups are simultaneously introduced by the functional group conversion of 3), or a combined method of 3) sequential introduction method and simultaneous introduction method. Thus, the method for producing a compound having two or more kinds of mesogenic groups is not particularly limited, and a known method can be appropriately used. For example, the method described in JP-A-2002-267838 May be adopted. Thus, the polymerizable liquid crystal compound can be produced by appropriately using a known method according to the type of the compound to be used. As other methods, Japanese translations of PCT publication No. 2010-522892, JP-T 2010-522893, JP-T 2010-537954, JP-T 2010-537955, JP-T 2010-540472, JP-T 2012- No. 532155, JP 2013-509458, JP 2007-2208, JP 2007-2209, JP 2007-2210, JP 2009-173893, JP 2010-30979. Gazette, JP2011-6360, JP2011-6361, JP2011-42606, JP2011-162678, JP2011-207765, JP2013-71956, JP 2005-289980 A, JP 2006-24347 A JP, 2008-273925, JP 2009-62508, JP 2009-179563, JP 2010-84032, JP 2005-208415, JP 2005-208416. And WO2012 / 169424.

  Moreover, you may utilize a commercial item as said polymeric liquid crystal compound. Further, such polymerizable liquid crystal compounds may be used alone or in a mixture of two or more. Moreover, when combining 2 or more types of liquid crystal compounds, it is not necessary for all the liquid crystal compounds to show liquid crystallinity, and a mixture should just show liquid crystallinity. For example, a compound having two or more kinds of mesogenic groups may have a liquid crystallinity with a mixture with another liquid crystal compound even if the compound itself does not exhibit liquid crystallinity. Further, when a mixture of two or more polymerizable liquid crystal compounds is used, it is not necessary that all the liquid crystal compounds have a polymerizable functional group, and at least one liquid crystal compound has a polymerizable functional group. That's fine.

  Moreover, such a polymerizable liquid crystal compound may use a mixture of a liquid crystal compound having a polymerizable group and another polymerizable monomer that does not exhibit liquid crystallinity. Such other polymerizable monomers are not particularly limited as long as they have compatibility with a liquid crystal compound having a polymerizable group and do not cause significant alignment inhibition when the liquid crystal compound is aligned. However, a known polymerizable monomer can be appropriately used, and a suitable monomer may be selected from the known polymerizable monomers according to the design of the target liquid crystal composition. Examples of such other polymerizable monomers include compounds having a polymerizable functional group such as an ethylenically unsaturated group (for example, vinyl group, vinyloxy group, (meth) acryloyl group). The addition amount of such other polymerizable monomer is 0.5 to 50% by weight with respect to the total amount of the liquid crystal compound having the polymerizable group and the other polymerizable monomer not exhibiting the liquid crystal property. Is preferable, and it is preferable to set it as 1 to 30 weight%. The number of polymerizable functional groups of such a polymerizable monomer is preferably 2 or more from the viewpoint of sufficiently increasing the polymerization rate and imparting sufficient heat resistance to the obtained liquid crystal film. . Furthermore, the method for producing such a polymerizable monomer is not particularly limited, and a known method can be appropriately used. Moreover, you may utilize a commercial item as such a polymerizable monomer.

  The polymerizable liquid crystal composition used in the present invention may contain a polymerization initiator for polymerizing the polymerizable liquid crystal compound as described above. The polymerization initiator is not particularly limited, and a known polymerization initiator can be appropriately used. From the known polymerization initiators, the above-mentioned polymerization can be performed more efficiently depending on the type of the polymerizable liquid crystal compound in the composition. What can start polymerization of a polymerizable liquid crystal compound may be appropriately selected and used.

  The polymerization initiator may be a thermal polymerization initiator (an initiator when using a thermal polymerization reaction) or a photopolymerization initiator (an initiator when using light or electron beam irradiation). Also good. As such a polymerization initiator, in the case of using a plastic film or the like as a base material when producing a liquid crystal film, from the viewpoint of preventing the base material and the like from being deformed or altered by heat, It is more preferable to use a photopolymerization initiator. Examples of such photopolymerization initiators include α-carbonyl compounds, acyloin ethers, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, triarylimidazole dimers and p-aminophenyl ketones. , Acridine and phenazine compounds and oxadiazole compounds. Examples of such α-carbonyl compounds include α-carbonyl compounds described in US Pat. No. 2,367,661 and US Pat. No. 2,367,670. Examples of the acyloin ether include US Pat. The thing etc. which are described in 2448828 specification are mentioned. Examples of the α-hydrocarbon substituted aromatic acyloin compound include those described in US Pat. No. 2,722,512. Examples of the polynuclear quinone compound include US Pat. No. 3,046,127 and US Pat. No. 2,951,758. And the like described in the specification. Examples of the combination of triarylimidazole dimer and p-aminophenylketone include those described in US Pat. No. 3,549,367, and the acridine and phenazine compounds include, for example, Examples described in JP-A-60-105667 and U.S. Pat. No. 4,239,850 are exemplified. Further, examples of the oxadiazole compound include those described in U.S. Pat. No. 4,212,970. .

  Moreover, as a photoinitiator, you may utilize a commercial item, for example, the photoinitiator made from BASF (brand name "Irgacure 907", brand name "Irgacure 651", brand name "Irgacure 184"). Alternatively, a photopolymerization initiator (trade name “UVI6974”) manufactured by Union Carbide may be used as appropriate. Such photopolymerization initiators include those that generate free radicals and those that generate ions upon irradiation with light or an electron beam, and the type and polymerization of the polymerizable liquid crystal compound in the composition. Depending on the reaction conditions and the like, a photopolymerization initiator that generates free radicals (for example, trade name “Irgacure 651” manufactured by BASF) or a photopolymerization initiator that generates ions (for example, Union Carbide manufactured by Union Carbide). A suitable photopolymerization initiator (trade name “UVI6974”)) may be appropriately selected and used.

  Further, the content of the polymerization initiator is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the composition (mixture) obtained by adding the dichroic dye to the polymerizable liquid crystal composition. More preferably, it is 5 parts by weight. When the content of the polymerization initiator is too small, the resulting retardation plate tends to have insufficient curability. On the other hand, when the content of the polymerization initiator is too large, the orientation of the liquid crystal tends to be defective. . When the content of the polymerization initiator is within the above numerical range, it is possible to suppress the occurrence of defects in the alignment of the liquid crystal and to obtain a highly curable retardation plate.

[Dichroic dye]
Next, the dichroic dye used in the present invention will be described. The dichroic dye as used herein refers to a dye having a property that the absorbance in the major axis direction of the molecule is different from the absorbance in the minor axis direction. The dichroic dye is not particularly limited as long as it has such properties, and may be a dye or a pigment. In the present invention, the dichroic dye is represented by the following formula (1), The order parameter (S) of the dichroic dye in the polymer is in the range of 0.4 ≦ S ≦ 1.0.
S = (DR-1) / (DR + 2) (1)
(In the formula (1), DR is an absorption dichroic ratio of the dichroic dye represented by the following formula (2).)
(In the formula (2), λ represents the wavelength (nm) of light in vacuum,
A _e (λ) represents a polarization absorption spectrum parallel to the slow axis in the polymer,
A _o (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the polymer,
A _e0 (λ) represents a polarization absorption spectrum parallel to the slow axis in a polymer obtained by polymerizing only the polymerizable liquid crystal composition excluding the dichroic dye,
A _o0 (λ) represents a polarized light absorption spectrum perpendicular to the slow axis in a polymer obtained by polymerizing only the polymerizable liquid crystal composition excluding the dichroic dye. )

  As described above, when a dichroic dye is added to a normal liquid crystal compound having no “negative dispersion” characteristic, the dichroic dye is aligned in the direction of the director of the liquid crystal molecules. However, in the liquid crystal compound having the “negative dispersion” characteristic used in the present invention, since the mesogen group is present in the direction substantially perpendicular to the direction of the director of the liquid crystal molecule as described above, the dichroism in the normal liquid crystal compound is present. Compared to the case where a dye is added, the orientation of the dichroic dye is lowered, and as a result, the dichroic ratio tends to be lowered. In the present invention, by using a dichroic dye having an order parameter (S) represented by the above formula (1) in a range of 0.4 ≦ S ≦ 1.0, “negative dispersion” is used. Even when it is added to a polymerizable liquid crystal composition having the characteristics, a high dichroic ratio can be maintained.

  The dichroic ratio of the dichroic dye is defined by the ratio of the absorbance at the maximum absorption wavelength in the major axis direction of the dye molecule to the absorbance in the minor axis direction. The dichroic ratio can be determined by measuring the absorbance in the orientation direction of the dye and the absorbance in the direction perpendicular to the orientation direction. The dichroic dye that can be used in the present invention has a dichroic ratio of preferably 2 to 50, more preferably 5 to 30.

  Such dichroic dyes are not particularly limited. For example, acridine dyes, azine dyes, azomethine dyes, oxazine dyes, cyanine dyes, merocyanine dyes, squarylium dyes, naphthalene dyes, azo dyes, anthraquinone dyes, benzotriazole dyes Benzophenone dye, pyrazoline dye, diphenyl polyene dye, binaphthyl polyene dye, stilbene dye, benzothiazole dye, thienothiazole dye, benzimidazole dye, coumarin dye, nitrodiphenylamine dye, polymethine dye, naphthoquinone dye, perylene dye, quinophthalone dye, stilbene dye Examples thereof include dyes and indigo dyes. Among these, the dichroic dye is preferably an anthraquinone dye or an azo dye. Examples of the azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and stilbene azo dyes, and preferred examples include bisazo dyes, trisazo dyes, and derivatives of these series of dyes. Any dye that satisfies the above conditions can be used in the present invention. An example of a dye that can be used in the present invention is represented by a dye number described in a dye handbook (Shin Okawara, Shinjiro Kitao, Tsuneaki Hirashima, Ken Matsuoka, Kodansha Scientific Co., Ltd .: 1986, 1st edition). It is shown in 1.

The dichroic dye is particularly preferably one represented by the following formula (1) (hereinafter sometimes referred to as “azo dye (1)”).

In the formula (1), n is an integer of 1 to 4, and Ar ₁ and Ar ₃ each independently represent a group selected from the following group.

In Formula (1), Ar ₂ represents a group selected from the following group. When n is 2 or more, Ar ₂ may be the same as or different from each other.

In the above groups, A ₁ and A ₂ each independently represent a group selected from the following group.
(In the formula, m is an integer of 0 to 10, and when there are two m's in the same group, these two m's may be the same or different from each other.)

  The positional isomerism of the azobenzene moiety of the azo dye (1) is preferably trans. Examples of the azo dye (1) include compounds represented by formulas (1-1) to (1-58).

  Among the specific examples of the azo dye (1) described above, Formula (1-2), Formula (1-5), Formula (1-6), Formula (1-8), Formula (1-10), Formula ( 1-12), Formula (1-13), Formula (1-15), Formula (1-16), Formula (1-19), Formula (1-20), Formula (1-21), Formula (1) -22), formula (1-23), formula (1-24), formula (1-26), formula (1-27), formula (1-28), formula (1-29), formula (1- 30) Formula (1-31), Formula (1-32), Formula (1-33), Formula (1-34), Formula (1-35), Formula (1-36), Formula (1-49) , Formula (1-50), Formula (1-51), Formula (1-52), Formula (1-53), Formula (1-54) Formula (1-55), Formula (1-56), Formula Those represented by (1-57) and formula (1-58) are more preferred. Formulas (1-2) and (1-5) , Formula (1-8), Formula (1-10), Formula (1-15), Formula (1-21), Formula (1-22), Formula (1-26), Formula (1-28), Formula (1-29), Formula (1-30), Formula (1-31), Formula (1-32), Formula (1-33), Formula (1-34), Formula (1-35) Formula ( 1-36), Formula (1-49), Formula (1-50), Formula (1-51), Formula (1-52), Formula (1-53), Formula (1-54), and Formula (1) -55) are particularly preferred.

As the anthraquinone dye, a compound represented by the formula (1-59) is preferable.
(In the formula, R ^{1 to} R ⁸ each independently represent a hydrogen atom, —Rx, —NH ₂ , —NHRx, —NRx ₂ , —SRx, or a halogen atom. Rx has 1 to 4 carbon atoms. Represents an alkyl group or an aryl group having 6 to 12 carbon atoms.)

Moreover, as an acridine pigment | dye, the compound represented by Formula (1-60) is preferable.
(In the formula, R ^{9 to} R ¹⁵ each independently represent a hydrogen atom, —Rx, —NH ₂ , —NHRx, —NRx ₂ , —SRx or a halogen atom. Rx has 1 to 4 carbon atoms. Represents an alkyl group or an aryl group having 6 to 12 carbon atoms.)

As the oxazone dye, a compound represented by the formula (1-61) is preferable.
(In the formula, R ^{16 to} R ²³ each independently represent a hydrogen atom, —Rx, —NH ₂ , —NHRx, —NRx ₂ , —SRx, or a halogen atom. Rx has 1 to 4 carbon atoms. Represents an alkyl group or an aryl group having 6 to 12 carbon atoms.)

  In the above formula (1-59), formula (1-60) and formula (1-61), the alkyl group having 1 to 6 carbon atoms of Rx is a methyl group, an ethyl group, a propyl group, a butyl group, or pentyl. A aryl group having 6 to 12 carbon atoms, such as a phenyl group, a toluyl group, a xylyl group, and a naphthyl group.

Moreover, as a cyanine pigment | dye, the compound represented by Formula (1-62) and the compound represented by Formula (1-63) are preferable.
(In the formula, D ¹ and D ² each independently represent a group represented by any of the following formulas (1-62a) to (1-62d), and n5 represents an integer of 1 to 3. .)

(In Formula (1-63), D ³ and D ⁴ each independently represent a group represented by any of the following Formulas (1-63a) to (1-63h); Represents an integer of 3.)

  As mentioned above, although the preferable example was demonstrated about the dichroic dye which the said phase difference plate contains, it is preferable that it is an azo dye (1) as a dichroic dye, and an azo dye which has mutually different maximum absorption wavelength. You may contain at least 2 types (1).

  Such a dichroic dye may have a polymerizable functional group and may have liquid crystallinity. As the polymerizable functional group, an acrylic group, a methacryl group, a vinyl group, a vinyloxy group, an epoxy group, and an oxetanyl group are preferable, and an acrylic group, an epoxy group, and an oxetanyl group are particularly preferable from the viewpoint of reactivity. As for the liquid crystallinity, those having a nematic phase and a smectic phase are preferable.

  Among the dichroic dyes having the order parameter (S) in the range of 0.4 ≦ S ≦ 1.0, the dichroic dye is a rod-like molecule, and the molecular length in the long axis direction is 2 nm to Those having a thickness of 10 nm can be preferably used. Here, “the molecular length in the major axis direction” means the longest distance among the interatomic distances excluding the non-cyclic functional groups and hydrogen atoms present at both ends of the dichroic dye compound. The cyclic functional group is a linear aliphatic hydrocarbon group, vinyl group, carbonyl group, alcohol group, alkoxy group, ether group and the functional group connected with a non-cyclic aliphatic hydrocarbon group, and the functional group. In which a hydrogen atom is substituted with a halogen atom, and does not include an aromatic ring group, an unsaturated heterocyclic group, or an aliphatic ring group. Density functional method (DFT method) using the quantum chemistry calculation package (ORCA Ver 3.0.1) in the initial configuration with a conformation that maximizes the molecular length (for example, trans configuration for molecules having an azo group) The molecular length can be calculated by performing the most stable structure calculation. Further, PBE0 can be used as the functional, and Def2-SVP can be used as the basis. Even when a dichroic dye having a molecular length of 2 nm to 10 nm is used, even when added to a liquid crystal compound having a characteristic of “negative dispersion” having a mesogenic group in a direction substantially perpendicular to the director of the liquid crystal molecule, The dichroic dye can be oriented in the direction of the director, and the order parameter (S) can approach 1.0.

  The dichroic dye preferably has a maximum absorption wavelength (λmax) in the range of 400 to 780 nm, more preferably 450 to 700 nm, and even more preferably 540 to 650 nm. In the case of application to an apparatus, it is preferable to select an absorption maximum wavelength that is different from the absorption maximum wavelength of the emission spectrum of the image display device in consideration of the emission spectrum of the light source of the image display device.

  For example, when the retardation plate of the present invention is applied to an organic electroluminescence display device having three emission spectra of red, blue, and green that have maximum values at about 460 nm, about 530 nm, and about 630 nm, respectively, In order to minimize the decrease in the transmittance due to this absorption, it is necessary to select a dichroic dye having a maximum absorption at a wavelength outside the maximum wavelength of the emission spectrum of these three colors. For example, it is preferable to apply a dichroic dye having a maximum absorption wavelength in the vicinity of 580 nm as shown in FIG. FIG. 11 shows the emission spectrum of the organic electroluminescence display device, but the same applies to other image display devices. For example, in a liquid crystal display device, when an LED is used as a light source, the decrease in transmittance is reduced by setting the wavelength that deviates from the maximum value of the emission spectrum of the LED that uses the absorption maximum wavelength of the dichroic dye. Can do. The difference between the absorption maximum wavelength of the dichroic dye and the maximum wavelength of the emission spectrum of the image display device is 5 nm or more, preferably 10 nm or more, and more preferably 20 nm or more. If it is less than 5 nm, suppression of the transmittance | permeability fall by removing a wavelength will become inadequate.

  The content of the dichroic dye in the retardation plate can be adjusted as appropriate according to the type of the dichroic dye. In the present invention, the order parameter (S) is 0.4 ≦ S ≦ 1. Since a dichroic dye in the range of 0 is used, a high reverse dispersibility improving effect can be maintained while suppressing the content of the dichroic dye. Specifically, it is 0.03 to 0.8 part by weight and preferably 0.05 to 0.5 part by weight with respect to 100 parts by weight of the polymerizable liquid crystal composition. In this invention, since content of a dichroic dye can be made into the above ranges, the transmittance | permeability fall of a phase difference plate by adding a dichroic dye can be suppressed. In addition, content of dichroic pigment | dye here means the total amount, when two or more types of dichroic pigment | dye are included.

<Method for producing retardation plate>
Next, a method for producing a retardation plate according to the present invention will be described. The method for producing a retardation plate is not limited to these, but a composition containing a polymerizable liquid crystal composition, a dichroic dye and various compounds added as necessary is in a molten state, or The composition solution is applied onto an alignment substrate to form a coating film, and then the coating film is dried, heat-treated (liquid crystal alignment), or, if necessary, light irradiation and / or heat treatment (polymerization / crosslinking) By fixing the parallel alignment using the above-described means for fixing the alignment, the optically anisotropic layer in which the alignment of the liquid crystal and the dichroic dye is fixed is formed.

  The state that “the alignment state is fixed in the state of parallel alignment” is a state in which the parallel alignment (the major axis of the liquid crystal molecules is observed in the optically anisotropic layer obtained by polymerizing the polymerizable liquid crystal composition and fixing the alignment. Means that the orientation is aligned in a direction substantially parallel to the substrate), and a component derived from a polymerizable liquid crystal compound (preferably a component derived from a polymerizable liquid crystal compound: Any one of the polymerizable liquid crystal compound itself, a composition formed by decomposing the polymerizable liquid crystal compound, a polymer of the polymerizable liquid crystal compound, etc.) is fixed in a parallel alignment state. Just do it. The orientation indicates a state in which the molecular chains of the liquid crystal compound are aligned in a specific direction, and this state can be measured by measuring the phase difference (Δn · d) of the film. For example, Δn · d indicates 20 nm or more at a measurement wavelength of 550 nm. Δn · d is the product of the birefringence Δn and the film thickness d of the liquid crystal film.

  The solvent used for preparing the solution is not particularly limited as long as it can dissolve the polymerizable liquid crystal composition and the dichroic dye and can be distilled off under appropriate conditions. Generally, acetone, methyl ethyl ketone, isophorone, cyclohexanone, cyclohexane Ketones such as pentanone, alcohols such as isopropyl alcohol and n-butanol, ether alcohols such as butoxyethyl alcohol, hexyloxyethyl alcohol and methoxy-2-propanol, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 2-methoxyethyl acetate Glycol ethers such as propylene glycol 1-monomethyl ether 2-acetate, esters such as ethyl acetate and ethyl lactate, phenols such as phenol and chlorophenol, N, -Amides such as dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, halogenated hydrocarbons such as chloroform, dichloromethane, trichloroethylene, tetrachloroethane, tetrachloroethane, tetrachloroethylene, chlorobenzene, dichlorobenzene, etc., tetrahydrofuran, Heterocycles such as γ-butyrolactone, aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc. Preferably used.

  Moreover, as such a solvent, it is suitable with respect to the drying rate suitable for apply | coating a solution so that it may become a uniform film thickness, handling ease (harmful to environment), a polymerizable liquid crystal composition, and a dichroic dye. From the viewpoint of solubility, propylene glycol 1-monomethyl ether 2-acetate, 2-methoxyethyl acetate, toluene, xylene, methoxybenzene, 1,2-methoxybenzene, cyclohexanone, cyclopentanone, methyl cellosolve, ethyl cellosolve, butyl cellosolve, γ-butyrolactone is preferred, and propylene glycol 1-monomethyl ether 2-acetate, toluene, and γ-butyrolactone are more preferred. In addition, you may utilize 1 type as such a solvent individually or in combination of 2 or more types. Further, depending on the type of the base material, corrosion may occur depending on the type of the solvent. Therefore, it is preferable to appropriately select and use a suitable solvent according to the type of the base material.

  In addition, as the content of the solvent used in the present invention, the usage method of the composition (for example, when used for forming an optically anisotropic layer, the design of the thickness, the coating method, etc. are also included. It differs depending on the method of use etc.) and cannot be generally specified, but it is preferably 30 to 98% by weight, more preferably 50 to 95% by weight, and 70 to 90% by weight. Is more preferable. If the content of such a solvent is too small, the amount of the solvent with respect to the mixture of the polymerizable liquid crystal composition and the dichroic dye decreases, so that liquid crystal is deposited during storage or the viscosity of the mixture increases. Since the wetting property is lowered, it tends to be difficult to perform coating during the production of the retardation plate. On the other hand, if the content of the solvent is too high, it takes a long time to remove the solvent (drying time), and not only the work efficiency is reduced when the film is produced, but the mixture is coated on the substrate. In this case, since the surface flow becomes intense, it tends to be difficult to use the composition in order to produce a uniform retardation plate. Thus, in the mixture (composition) of the polymerizable liquid crystal composition and the dichroic dye, the amount of the mixture of components other than the solvent is preferably 2 to 70% by weight, and 5 to 50%. It is more preferable that it is weight%, and it is still more preferable that it is 10-30 weight%. In addition, in the mixture of the polymerizable liquid crystal composition and the dichroic dye, not only the above-described solvent but also a reaction activator, a sensitizer, and a surfactant are used to form a uniform coating film on the alignment substrate. An antifoaming agent, a leveling agent, etc. may be added.

  Next, an alignment substrate for aligning the polymerizable liquid crystal composition will be described. As the alignment substrate, a substrate having a smooth plane is preferable, and examples thereof include a film or sheet made of an organic polymer material, a glass plate, and a metal plate. From the viewpoint of cost and continuous productivity, it is preferable to use a material made of an organic polymer. Examples of organic polymer materials include polyvinyl alcohol, polyimide, polyamide, polyamideimide, polyphenylene sulfide, polyether sulfone, polyphenylene oxide, polyether ketone, polyether ether ketone, polyethylene terephthalate, polyethylene naphthalate, polysulfone, polyarylate. Examples thereof include polyester polymers such as cellulose polymers such as diacetylcellulose and triacetylcellulose, polycarbonate polymers, acrylic polymers such as polymethylmethacrylate, and transparent polymers such as epoxy resins and phenol resins. Also, styrene polymers such as polystyrene, acrylonitrile / styrene copolymer, olefin polymers such as polyethylene, polypropylene, ethylene / propylene copolymer, cyclopolyolefins having cyclic or norbornene structure, vinyl chloride polymers, nylon and aromatic polyamides. Examples thereof include a film made of a transparent polymer such as an amide polymer. Furthermore, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers Examples thereof include a film made of a transparent polymer such as a polymer, an epoxy-based polymer, and a blend of the above polymers.

  As the cellulose polymer, a lower fatty acid ester of cellulose is more preferable. As such a lower fatty acid, a fatty acid having 6 or less carbon atoms is preferable. The number of carbon atoms of such lower fatty acids is more preferably 2-4. Examples of such a cellulose polymer include cellulose acetate, cellulose propionate, and cellulose butyrate. Among such cellulose polymers, cellulose triacetate is particularly preferable. As the cellulose polymer, a mixed fatty acid ester such as cellulose acetate propionate or cellulose acetate butyrate may be used.

  Examples of the cyclic olefin polymer (COP) include cyclic olefin ring-opening polymers, cyclic olefin addition polymers, random copolymers of cyclic olefins and α-olefins such as ethylene and propylene, and the like. Examples include graft-modified products modified with saturated carboxylic acid and derivatives thereof, and hydrides thereof. Moreover, as such a cyclic olefin, norbornene, its derivative (s), and dicyclopentadiene are preferable. Commercially available products can also be used as the cyclic olefin polymer film. For example, ZEONOR (trade name, manufactured by ZEON CORPORATION), ZEONEX (trade name, manufactured by ZEON CORPORATION), Arton (trade name, JSR Corporation) ))) Can be used.

  Among the films made of the organic polymer materials described above, plastic films such as triacetyl cellulose, polycarbonate, norbornene polyolefin, and polyethylene terephthalate used as an optical film can be preferably used. Moreover, as a metal film, the said film formed from aluminum etc. is mentioned, for example.

  Further, such a base material is not particularly limited, but depending on its use in the case of using a laminated body of an optically anisotropic layer and a base material as it is for an optical film or the like as it is. Thus, it may have a phase difference function. Further, such a substrate may be uniaxially stretched (so-called uniaxially stretched film) or biaxially stretched (so-called biaxially stretched film). Such a base material may be used as a film having optical anisotropy by developing biaxial optical anisotropy by stretching the base material in the vertical direction and the horizontal direction.

  Moreover, as such a base material, a substrate that has been subjected to a Z-axis alignment treatment may be used. Furthermore, such a substrate may be appropriately subjected to surface treatment such as corona treatment, plasma treatment, UV-ozone treatment, saponification treatment, etc. on one or both sides for the purpose of controlling the adhesiveness. The treatment conditions for adopting such a surface treatment may be appropriately set according to the base material to be used, and are not particularly limited, and known conditions may be appropriately adopted.

  Some of these films exhibit sufficient alignment ability for the polymerizable liquid crystal composition without performing a treatment for expressing the alignment ability again depending on the production method. If not shown, etc., if necessary, these films are stretched under moderate heating, or the film surface is rubbed in one direction with a rayon cloth or the like, or a so-called rubbing treatment is performed on the film. An alignment film made of a known alignment agent such as an alcohol or a silane coupling agent is provided to perform rubbing treatment, or a photo-alignment film is applied on the film and heated at an appropriate temperature, and then irradiated with linearly polarized ultraviolet light. It is also possible to use a film that exhibits orientation ability by forming a film, performing oblique vapor deposition treatment of silicon oxide or the like, or appropriately combining these means.

  In addition, aluminum, iron, copper, nickel, stainless steel and other metal plates provided with regular fine grooves on the surface, various glass plates, etc., or those as master molds, the regular fine grooves were thermally transferred to the film surface. Those having a regular fine groove transferred onto the film surface using a UV curable resin or the like can also be used as the alignment substrate. Among these, in the field of liquid crystal, it is common to perform a rubbing process by rubbing the substrate with a cloth or the like. An important setting value that defines the rubbing condition is a peripheral speed ratio. This represents the ratio between the movement speed of the cloth and the movement speed of the substrate when the rubbing cloth is wound around a roll and rubbed while the substrate is rubbed. In the present invention, the peripheral speed ratio is usually 50 or less, more preferably 25 or less, and particularly preferably 10 or less. When the peripheral speed ratio is larger than 50, the effect of rubbing is too strong, and the liquid crystal material cannot be completely aligned, and alignment may be insufficient, leading to characteristic deterioration.

  Next, a method for applying a mixture (composition) containing a polymerizable liquid crystal composition and a dichroic dye to the above-described alignment substrate will be described. The application method is not particularly limited as long as the uniformity of the coating film is ensured, and a known method can be adopted. Examples thereof include spin coating, die coating, curtain coating, dip coating, and roll coating. Such a coating film varies depending on the content of the solvent in the mixture of the polymerizable liquid crystal composition and the dichroic dye, etc., and although it cannot be generally stated, the thickness of the coating film before drying (wet (Film thickness) is preferably 3 to 50 μm, more preferably 5 to 20 μm. If the thickness (wet film thickness) is too small, it is necessary to increase the concentration of the solid content (liquid crystal compound or the like) in the liquid crystal composition in order to obtain desired optical characteristics. Of the liquid crystal film is liable to occur and it becomes difficult to obtain a uniform liquid crystal film, and uniform coating is also difficult, and the smoothness of the liquid crystal film tends to decrease. On the other hand, when the thickness (wet film thickness) is too large, the concentration of the solid content in the liquid crystal composition for obtaining desired optical characteristics becomes thin, so that the drying time after coating tends to be long.

  The method of applying the liquid crystal material solution preferably includes a drying step for removing the solvent after the application. The drying conditions differ depending on the polymerizable liquid crystal composition, the dichroic dye, the type of the solvent, and the like, and are not generally described, and are not particularly limited. For example, depending on the type of solvent, the solvent can be removed from the coating film even at room temperature (25 ° C.). Thus, depending on the type of the solvent, it is possible to produce a parallel aligned liquid crystal film without any particular heat treatment. Moreover, as temperature conditions in such a solvent removal process, it is preferable that it is 15-110 degreeC, and it is more preferable that it is 20-80 degreeC. In order to dry at a temperature below 15 ° C., a separate cooling facility may be required. On the other hand, if the substrate is dried at a high temperature, the base material may be distorted by heat and optical characteristics and the like may be changed, and desired optical characteristics may not be obtained.

  Moreover, it does not restrict | limit especially as a pressure condition in this drying process, However, It is preferable that it is 650-1400 hPa, and it is more preferable that it is 900-1100 hPa. When the pressure condition is less than the lower limit, the solvent is rapidly dried and uneven drying tends to occur. On the other hand, when the upper limit is exceeded, the solvent tends to take longer to dry. Although it does not restrict | limit especially as time (drying time) of such a solvent removal process, It is preferable to set it as 10 seconds-60 minutes, and it is more preferable to set it as 30 seconds-30 minutes. If the drying time is less than the lower limit, the solvent is rapidly dried, and the smoothness of the liquid crystal film tends to be reduced (drying unevenness occurs). Tend to decrease. In addition, when using a drying apparatus for such a solvent removal process, control the relative moving speed of the said coating film and drying apparatus so that a relative wind speed may be 60m / min-1200m / min. Is preferred. Any known method can be employed without particular limitation as long as the uniformity of the coating film is maintained. For example, a method such as a heater (furnace) or hot air blowing may be used.

  The film thickness in the dry state of the applied film is preferably 0.1 μm to 50 μm, more preferably 0.2 μm to 20 μm. Outside this range, the optical performance of the obtained optically anisotropic layer may be insufficient, or the alignment of the polymerizable liquid crystal composition and the dichroic dye may be insufficient.

  Next, a method for fixing the orientation will be described. As a method for polymerizing the polymerizable liquid crystal composition to fix the alignment state, a known polymerizable method can be appropriately employed depending on the type of the polymerization initiator and the polymerizable liquid crystal composition used. As a method for fixing such an alignment state (polymerization / fixation), for example, depending on the type of the polymerization initiator or the like, a polymerizable group (reactive functional group) can be obtained by performing light irradiation and / or heat treatment. It is also possible to adopt a method in which the orientation is fixed in a parallel orientation state by reacting the group).

When the polymerization initiator is such that it exhibits the function of an initiator by light irradiation (for example, in the case of a so-called photo radical initiator or photo cation generator), the alignment state of parallel alignment is fixed by light irradiation. Is preferable. The light irradiation method is not particularly limited. For example, a light source having a spectrum in the absorption wavelength region of the polymerization initiator used (for example, a metal halide lamp, an intermediate pressure or a high pressure mercury lamp having an illuminance of 10 mW / cm ² or more. (A medium pressure or high pressure mercury ultraviolet lamp), an ultra high pressure mercury lamp, a low pressure mercury lamp, a xenon lamp, an arc lamp, an LED, a laser, or the like) may be used. In addition, it becomes possible to activate a polymerization initiator by such light irradiation, and it becomes possible to react a reactive functional group efficiently.

Further, in such a light irradiation method, the integrated light irradiation amount is preferably 10 to 2000 mJ / cm ² and more preferably 100 to 1500 mJ / cm ² as the integrated exposure amount at a wavelength of 365 nm. preferable. However, this is not the case when the absorption region of the polymerization initiator and the spectrum of the light source are significantly different, or when the polymerizable liquid crystal compound itself has the ability to absorb light of the light source wavelength. In that case, from the viewpoint of fixing (curing) the coating film while maintaining the orientation state more efficiently, an appropriate photosensitizer and two or more polymerization initiators having different absorption wavelengths are mixed. It is also possible to adopt a method such as Moreover, the temperature condition at the time of such light irradiation should just be made into the temperature range in which the said polymeric liquid crystal compound can maintain the alignment state of a parallel alignment, and is not restrict | limited in particular. A cold mirror or other cooling device may be provided between the substrate and the light source (such as an ultraviolet lamp) so that the surface temperature of the coating film can maintain the range of the liquid crystal temperature during light irradiation.

  Furthermore, the atmospheric conditions at the time of light irradiation are not particularly limited, and may be an air atmosphere, or may be a nitrogen atmosphere in which oxygen is blocked in order to increase reaction efficiency. Since the oxygen concentration in the atmosphere is related to the degree of polymerization, when the desired degree of polymerization is not reached in the air, it is preferable to perform light irradiation in an atmosphere in which the oxygen concentration is reduced by a method such as nitrogen substitution. In such a case, the oxygen concentration in the atmospheric gas is preferably 10% by volume or less, more preferably 7% by volume or less, and most preferably 3% by volume or less.

  Further, when the polymerization initiator is such that the function of the initiator is expressed by heat (for example, in the case of a so-called thermal radical initiator or thermal cation generator), it is aligned in a parallel alignment state by heat treatment. Is preferably immobilized. The conditions for such heat treatment are not particularly limited, and the temperature conditions may be selected so that the orientation state is sufficiently maintained according to the type of the polymerization initiator, and known conditions are appropriately employed. be able to. In addition, when using a thing with low heat resistance as an alignment base material, the thing which expresses the function of an initiator by light irradiation is used as a polymerization initiator, and the alignment state of parallel alignment is fixed by light irradiation. It is preferable.

  The liquid crystal film produced by the above process is a sufficiently strong film. Specifically, the mesogens are three-dimensionally bonded by the curing reaction, and not only the heat resistance (the upper limit temperature for maintaining the liquid crystal alignment) is improved as compared to before curing, but also scratch resistance, abrasion resistance, crack resistance. The mechanical strength such as property is also greatly improved.

  As described above, after applying the mixture (composition) containing the polymerizable liquid crystal composition and the dichroic dye on the alignment substrate, the solvent is removed from the coating film, and the polymerizable liquid crystal composition and the dichroic color are then removed. By aligning the crystalline dye and fixing the liquid crystal state, a liquid crystal film in which the alignment state is fixed in a parallel alignment state can be formed on the alignment substrate.

  As the alignment substrate, it is not optically isotropic, or the obtained retardation plate is finally opaque in the intended use wavelength region, or the alignment substrate is too thick, which hinders actual use. When there is a problem such as occurrence, an optically isotropic substrate, a stretched film having a retardation function, or a form directly transferred to a polarizing plate can be used from the form formed on the alignment substrate. As a transfer method, a known method can be adopted. For example, as described in JP-A-4-57017 and JP-A-5-333313, a liquid crystal film is laminated on a substrate different from the alignment substrate via an adhesive or an adhesive, and then, if necessary, adhesive Examples include a method of transferring only the liquid crystal film by performing a surface curing treatment using an agent or an adhesive and peeling the alignment substrate from the liquid crystal film.

  The pressure-sensitive adhesive or adhesive used for transfer is not particularly limited as long as it is of optical grade, and generally used ones such as acrylic, epoxy, and urethane can be used. In addition, it is possible to use the liquid crystal film alone as the element, but in order to improve the strength and durability of the liquid crystal film, the retardation plate is covered with a transparent protective layer on one or both sides of the liquid crystal film. It can also be configured. Examples of the transparent protective layer include those obtained by laminating transparent plastic films such as polyester and triacetyl cellulose directly or via an adhesive, resin coating layers, acrylic and epoxy photocurable resin layers, and the like. It is done. When these transparent protective layers are coated on both sides of the liquid crystal film, different protective layers may be provided on both sides. Moreover, as an optically anisotropic element, a liquid crystal film can be directly formed on a polarizing plate, and the elliptically polarizing plate of this invention can be used as it is. For example, after laminating a liquid crystal film on a transparent plastic film such as polyester or triacetyl cellulose used for producing the polarizing film, the polarizing film / transparent plastic film / retardation plate (liquid crystal film) is integrated with the polarizing film. ) Or a polarizing film / phase difference plate (liquid crystal film) / transparent plastic film.

  As a method for confirming parallel alignment in the liquid crystal film obtained as described above, the following method may be employed. As a method for confirming the parallel alignment, a known method can be appropriately employed, and is not particularly limited. However, a pair of orthogonal polarizing plates (the direction in which one deflector deflects and the direction in which the other deflector deflects) Using a sample in which a liquid crystal film (which may be in the form of a laminate with a base material) is disposed between a pair of vertical polarizing plates), a method and a method for confirming transmitted light with the naked eye You may employ | adopt the method of observing a phase difference plate with a polarizing microscope. In any of the above methods, when the liquid crystal film is a parallel-aligned liquid crystal film, if light is incident from a direction perpendicular to the surface of the liquid crystal film in the sample, the phase difference of the light causes On the other hand, the amount of transmitted light when the incident angle of the light incident on the sample is tilted appears almost the same brightness in the direction opposite to the vertical direction. Therefore, the presence or absence of parallel orientation can be confirmed by measuring the brightness of such a sample through the naked eye or a polarizing microscope while shifting the incident angle of light. In addition, since the parallel alignment liquid crystal film has different phase difference characteristics depending on the incident angle of light as described above, a method for confirming parallel alignment is, for example, perpendicular to the surface of the liquid crystal film. A birefringence measuring device (for example, manufactured by Axo-metrix) capable of measuring a phase difference in a direction (perpendicular incident angle) and a phase difference when the incident angle of light is tilted from the vertical incident angle to a specific angle. Using the product name “Axoscan”, the product name “KOBRA-21ADH” manufactured by Oji Scientific Instruments, etc.), the angle is increased from 0 ° (perpendicular to the liquid crystal film) to a larger viewing angle. The phase difference is measured while appropriately changing, the phase difference of the sample is obtained at each of a plurality of viewing angles, and the phase difference is confirmed in a direction perpendicular to the surface of the liquid crystal film. Method for confirming the presence or absence of parallel orientation based on confirming that the phase difference in the direction in which the viewing angle becomes larger with respect to the value of the viewing angle is symmetrical with respect to each other. May be adopted.

  The thickness of the liquid crystal film (thickness of the cured film) is preferably 0.1 to 10 μm, more preferably 0.2 to 5 μm, although it varies depending on the application and required characteristics. If the thickness of the liquid crystal film is too small, the desired retardation may not be exhibited. On the other hand, if the thickness is too large, the orientation of the liquid crystal is decreased or the transmission due to the dye tends to be decreased.

[Elliptically polarizing plate]
According to this invention, the elliptically polarizing plate provided with the above-mentioned phase difference plate and a polarizing plate is provided. As the linear polarizing plate used in combination with the retardation plate, one having a protective film on one side or both sides of the polarizer is usually used. The polarizer is not particularly limited, and various types can be used. For example, for a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene / vinyl acetate copolymer partially saponified film. And polyene-based oriented films such as those obtained by adsorbing dichroic substances such as iodine and dichroic dyes and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, those obtained by stretching a polyvinyl alcohol film and adsorbing and orienting a dichroic material (iodine, dye) are preferably used. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  The protective film provided on one side or both sides of the polarizer is preferably one that is excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, isotropic properties, and the like. Examples of the material for the protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymers, and the like. Examples thereof include styrene polymers such as (AS resin), polycarbonate polymers, and the like. Also, polyolefin polymers such as polyethylene, polypropylene, ethylene / propylene copolymers, polyolefins having cycloolefin or norbornene structures, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfones Polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or Examples of the polymer that forms the protective film include blends of the aforementioned polymers. Other examples include films made of thermosetting or ultraviolet curable resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone. Generally the thickness of a protective film is 500 micrometers or less, and 1-300 micrometers is preferable. In particular, the thickness is preferably 5 to 200 μm.

  The protective film is preferably an optically isotropic substrate. For example, a triacetyl cellulose (TAC) film such as Fujitac (product of Fujifilm) or Konicatak (product of Konica Minolta Opto), Arton film (product of JSR) And cycloolefin polymers such as ZEONOR film and ZEONEX film (product of Nippon Zeon), acrylic film, TPX film (product of Mitsui Chemicals), and acrylprene film (product of Mitsubishi Rayon) From the viewpoint of flatness, heat resistance, moisture resistance, etc., triacetyl cellulose, cycloolefin polymer, and acrylic polymer are preferable.

  In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other via a water-based pressure-sensitive adhesive or an ultraviolet curable adhesive. Examples of aqueous adhesives include polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, aqueous polyurethanes, aqueous polyesters, and the like. Moreover, from a thin viewpoint, the board | substrate used for the phase difference plate which consists of a liquid crystal film may serve as the protective film of a polarizer.

  As the protective film, a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment subjected to diffusion or antiglare treatment can be used.

  Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, roughening by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a method or a compounding method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the protective film itself, or can be provided separately from the transparent protective layer as an optical layer.

  The retardation plate and the polarizing plate can be prepared by sticking each other through an adhesive layer. However, if the retardation plate is made of a liquid crystal film, the retardation plate and the polarizing plate are made of a polymerizable liquid crystal composition and a dichroic dye. The mixture (composition) can be produced by coating on an polarizer of a polarizing plate directly or through an alignment film and fixing the alignment. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer is appropriately used as a base polymer. Can be selected and used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  The pressure-sensitive adhesive layer can be formed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared. , A method in which it is directly attached on the liquid crystal layer by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on the separator according to the above and transferred onto the liquid crystal layer Examples include methods. The pressure-sensitive adhesive layer includes, for example, natural and synthetic resins, in particular, tackifier resins, glass fibers, glass beads, metal powder, fillers made of other inorganic powders, pigments, colorants, You may contain the additive added to adhesion layers, such as antioxidant. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  In addition, when bonding each optically anisotropic layer mutually through an adhesive layer, the film surface can be surface-treated and adhesiveness with an adhesive layer can be improved. The surface treatment means is not particularly limited, and a surface treatment method such as corona discharge treatment, sputtering treatment, low-pressure UV irradiation, or plasma treatment that can maintain the transparency of each optically anisotropic layer can be suitably employed. Among these surface treatment methods, corona discharge treatment is good.

[Image display device]
An image display device according to the present invention includes an elliptical (circular) polarizing plate including the above-described retardation plate and a polarizing plate. The type of the image display device is not particularly limited, and a known image display device such as a liquid crystal display device, an organic EL display device, or a plasma display can be appropriately used. Further, the method of arranging the elliptical (circular) polarizing plate in the image display device is not particularly limited, and a known method can be appropriately used.

[Liquid Crystal Display]
A liquid crystal display device to which the retardation plate according to the present invention is applied will be described. A liquid crystal display device is generally composed of a polarizing plate, a liquid crystal cell, and a retardation plate, a reflection layer, a light diffusion layer, a backlight, a front light, a light control film, a light guide plate, a prism sheet, and the like. In the present invention, there is no particular limitation except that the above-described retardation plate is used. The use position of the phase difference plate is not particularly limited, and may be one or a plurality of places. Moreover, it can also be used in combination with another phase difference plate.

  The liquid crystal cell is not particularly limited, and a general liquid crystal cell such as a liquid crystal layer sandwiched between a pair of transparent substrates provided with electrodes can be used. The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate in which the substrate itself has a property of orienting liquid crystals, a transparent substrate in which an alignment film having the property of orienting liquid crystals is provided, but the substrate itself lacks the alignment ability. Either can be used. Moreover, a well-known thing can be used for the electrode of a liquid crystal cell. Usually, it can be provided on the surface of the transparent substrate in contact with the liquid crystal layer, and when a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.

  The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystal substances, high-molecular liquid crystal substances, and mixtures thereof that can constitute various liquid crystal cells. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired. In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary to form various types of liquid crystal cells described later.

  As liquid crystal cell methods, TN (Twisted Nematic) method, STN (Super Twisted Nematic) method, ECB (Electrically Controlled Birefringence) method, IPS (In-Plane Switching) method, VA (Vertical Alignment) method, OCB (Optically Compensated) Birefringence method, HAN (Hybrid Aligned Nematic) method, ASM (Axially Symmetric Aligned Microcell) method, halftone gray scale method, domain division method, or display method using ferroelectric liquid crystal and antiferroelectric liquid crystal The method is mentioned.

  Also, the liquid crystal cell driving method is not particularly limited, and a passive matrix method used for STN-LCDs, etc., and an active matrix method using active electrodes such as TFT (Thin Film Transistor) electrodes and TFD (Thin Film Diode) electrodes, Any driving method such as a plasma addressing method may be used. The liquid crystal display device provided with the phase difference plate of the present invention has a desired birefringence wavelength dispersion characteristic because the phase difference plate has a desired birefringence wavelength dispersion characteristic. It is possible to improve the viewing angle and the image quality sufficiently.

[Organic electroluminescence equipment]
An organic electroluminescence device (organic EL display device) to which the retardation plate according to the present invention is applied will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.
In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror plate of the metal electrode can be completely shielded by forming the retardation plate with a quarter-wave plate and forming a circularly polarizing plate combining a linear polarizing plate and a retardation plate.
That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the retardation plate, but becomes circularly polarized light especially when the retardation plate is a quarter-wave plate and the angle between the polarization direction of the polarizing plate and the retardation plate is π / 4. .

  Circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded. When the angle between the absorption axis of the polarizing plate and the slow axis of the quarter-wave plate is defined as p in that a circular polarizing plate is formed by combining a quarter-wave plate with a linear polarizing plate, It is in the range of 40 ° to 50 °, preferably 42 to 48 °, more preferably about 45 °. In a range other than the above, there is a risk of image quality deterioration due to a decrease in the antireflection effect.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

In addition, each analysis method used in the Example is as follows.
(1) Alignment state of liquid crystal The alignment state of the liquid crystal was observed with an Olympus BH2 polarizing microscope.
(2) Refractive index Refractive indexes no and ne are measured using spectroscopic ellipsometry (manufactured by Horiba, Ltd., product name “AUTO-SE”) under conditions of a temperature of 20 ° C. ± 2 ° C. and a relative humidity of 60 ± 5%. A spectrum in the wavelength region of 440 to 1000 nm was measured.
(3) Birefringence measurement It measured using the automatic birefringence meter Axoscan by Axometrics.
(4) Polarization absorption spectrum and transmittance measurement of dichroic dye Measurement was performed using a spectroscopic spectrum (V-570) manufactured by JASCO Corporation.

<Preparation of dichroic dyes (D1) to (D6)>
[Dichroic dye (D1)]
25 g of 4-nitroaniline, 64 g of 35% hydrochloric acid and 60 mL of water were mixed and cooled to 5 ° C. or lower. A sodium nitrite solution consisting of 12.5 g of sodium nitrite and 60 mL of water was added dropwise to the solution at 5 ° C. After the addition, the reaction was carried out at 0 to 5 ° C. for 30 minutes to prepare a diazonium solution. The said diazonium solution was dripped at 5 degreeC to the solution which mixed phenol 17.5g, sodium acetate 60g, and water 300mL. After completion of the dropwise addition, the mixture was reacted at room temperature for 2 hours, and the produced crystals were filtered. The crystals were washed with water and then dissolved in ethanol. After concentration under reduced pressure, the crystals were dispersed with hexane and then filtered to obtain 39 g of 4-nitro-4′-hydroxyazobenzene represented by the following structural formula as a reddish brown crystal (yield 88%).

Next, after 24.9 g of 4-nitro-4′-hydroxyazobenzene was dissolved in 1500 mL of ethanol, a sodium sulfide solution consisting of 75 g of sodium sulfide nonahydrate, 240 mL of ethanol, and 240 mL of water was added dropwise at room temperature. After completion of dropping, the mixture was stirred at 50 ° C. for 3 hours. After completion of the reaction, the mixture was acidified with hydrochloric acid and extracted with ethyl acetate. The organic layer was washed with water and then saturated brine, dehydrated over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated under reduced pressure. Hexane was added to the concentrate for crystallization, followed by filtration to obtain 16.8 g of 4-amino-4′-hydroxyazobenzene represented by the following structural formula as a monoazo intermediate which was yellowish brown crystals (yield) 76%).

The monoazo intermediate (14.4 g), 35% hydrochloric acid (17.4 g) and water (210 mL) were mixed and cooled to 5 ° C. or lower. A sodium nitrite solution consisting of 5.25 g of sodium nitrite and 24 mL of water was added dropwise to the solution at 5 to 10 ° C. After the dropwise addition, reaction was carried out at 10 to 15 ° C. for 1 hour to prepare a diazonium solution. 9.0 g of 1-naphthylamine was dissolved in 180 g of methanol, and the diazonium solution was added dropwise at 5 to 10 ° C. After dropping, the mixture was stirred at room temperature for 12 hours, and insoluble matter was filtered and washed with water to obtain crystals. Extracted with methanol in the warm state, and the extract was concentrated and crystallized to give 4- [4- (4-hydroxyphenylazo) phenylazo] -1-naphthylamine represented by the following structural formula as a bisazo intermediate that was dark brown crystals. 6.6 g of crude product was obtained.

6 g of the bisazo intermediate crude product obtained as described above, 30 g of 35% hydrochloric acid and 150 g of DMF (N, N-dimethylformamide) were mixed and cooled to 5 ° C. or lower. A sodium nitrite solution consisting of 1.8 g of sodium nitrite and 18 mL of water was added dropwise to the solution at 0 ° C. After the dropwise addition, the mixture was reacted at 0 to 3 ° C. for 2 hours, and a solution consisting of 1.5 g of urea and 9 mL of water was added to prepare a diazonium solution. 3.6 g of N, N-diethylaniline was dissolved in 15 mL of DMF, and the diazonium solution was added dropwise at 0 ° C. After dripping, it reacted at 0-3 degreeC for 2 hours, the solution which consists of potassium carbonate 18g and water 90mL was added, and it filtered and washed with water, and obtained the crystal | crystallization. This was purified by column chromatography, and 4- [4- [4- (4- (4-hydroxyphenylazo) phenylazo] naphthylazo] -N, N-diethylaniline crude represented by the following structural formula as a trisazo intermediate which was a dark brown crystal. 2.0 g of product was obtained.

1.7 g of the trisazo intermediate obtained as described above, 1 g of 6-chlorohexyl acrylate (85% product), 0.8 g of potassium carbonate, BHT (2,6-di-tert-butyl-4-methylphenol) 0.01 g, potassium iodide 0.05 g, and NMP (N-methyl-2-pyrrolidone) 30 g were mixed and reacted at 85 ° C. for 3 hours. The reaction solution is cooled to 30 ° C., and 30 ml of water and 150 ml of ethyl acetate are added for liquid separation. The ethyl acetate layer is washed with saturated brine, dehydrated with magnesium sulfate and treated with activated carbon, and then the solvent is dried by concentration under reduced pressure. Solidified to obtain a black tar. This was purified by column chromatography with ethyl acetate, and 4- [4- [4- (4- (6-acryloyl)] represented by the following structural formula was obtained as a trisazo-based polymerizable dichroic dye (1) which is a black crystal. 150 mg of oxyhexyloxy) phenylazo) phenylazo] naphthylazo] -N, N-diethylaniline were obtained.

  The HPLC purity of the obtained dichroic dye (D1) was 99.8%, and the absorption maximum wavelength was 560 nm. Further, liquid crystallinity was exhibited from 122 ° C. to 200 ° C. (partially decomposed). Further, when the liquid crystallinity was confirmed, the crystal changed into a liquid crystal phase at 122 ° C. when the temperature was raised, and changed from the liquid crystal phase to the isotropic phase at 200 ° C. (partially decomposed). When the temperature dropped, it changed from an isotropic phase to a liquid crystal phase at 191 ° C., and showed liquid crystallinity up to room temperature.

  The molecular length of the compound was evaluated from the three-dimensional structure of the molecule obtained by quantum chemical calculation. For the azo group, the conformation that maximizes the molecular length of the trans-type for the other sites and the density functional method (DFT method) using the quantum chemistry calculation package (ORCA Ver 3.0.1) in the initial configuration The most stable structure was implemented. The functional was PBE0, and the basis was Def2-SVP. The calculated molecular length of the compound (the distance from the leftmost carbon atom of the leftmost benzene ring to the rightmost carbon atom of the rightmost benzene ring) was 2.15 nm.

[Dichroic dye (D2)]
As a dichroic dye (D2), a dye represented by the following formula (KRD-503, absorption maximum wavelength 570 nm, manufactured by Showa Kako) was prepared.
The molecular length (distance from the leftmost carbon atom of the leftmost benzene ring to the rightmost carbon atom of the rightmost benzene ring) calculated in the same manner as above was 2.33 nm.

[Dichroic dye (D3)]
4- (6-acryloyloxyhexyloxy) benzoic acid (1.5 g), tetrahydrofuran (100 mL) and triethylamine (5.2 g) were mixed and cooled to -30 ° C. To this solution, 3.5 g of the trisazo intermediate 4- [4- [4- (4-hydroxyphenylazo) phenylazo] naphthylazo] -N, N-diethylaniline synthesized in Synthesis Example 1 was added to 50 mL of tetrahydrofuran. The dissolved solution was added dropwise at −30 ° C., and then reacted at room temperature for 14 hours. The reaction solution was filtered and concentrated under reduced pressure to obtain 2.2 g of a dried solid product. This was purified by column chromatography with methylene chloride to obtain 0.6 g of crystals. This was crystallized with hexane and ethyl acetate, and recrystallized three times with a mixed solvent of methylene chloride and methanol, and represented by the following structural formula as a trisazo dichroic dye (D3) as 0.3 g of black crystals. 0.3 g of the compound obtained was obtained.

  The HPLC purity of the obtained dichroic dye (D3) was 98.5%, and the absorption maximum wavelength was 550 nm. As a result of confirmation of liquid crystallinity, the crystal changed from a crystal to a liquid crystal phase at 157 ° C. when the temperature was raised, and changed from a liquid crystal phase to an isotropic phase at 265 ° C. (decomposition). The molecular length of the compound calculated in the same manner as described above (the distance from the leftmost carbon atom of the leftmost benzene ring to the rightmost carbon atom of the rightmost benzene ring) was 2.78 nm.

[Dichroic dye (D4)]
As a dichroic dye (D4), a dye represented by the following formula (absorption maximum wavelength 580 nm) was prepared.
The molecular length (distance from the carbon atom at the 5-position of the leftmost indole ring to the rightmost nitrogen atom) of the compound calculated in the same manner as described above was 1.31 nm.

[Dichroic dye (D5)]
As a dichroic dye (D5), a dye represented by the following formula (Sudan Black B (CI 26150) manufactured by Tokyo Chemical Industry Co., Ltd., absorption maximum wavelength 600 nm) was prepared.
The molecular length of the compound calculated in the same manner as described above (the distance from the leftmost carbon atom of the leftmost benzene ring to the rightmost of the rightmost naphthalene ring) was 1.73 nm.

[Dichroic dye (D6)]
As a dichroic dye (D6), a dye represented by the following formula (D37 manufactured by NEMATEL, absorption maximum wavelength 540 nm) was prepared.
The molecular length (the distance from the leftmost carbon atom of the leftmost benzene ring to the rightmost carbon atom of the rightmost benzene ring) of the compound calculated in the same manner as described above was 1.59 nm.

[Dichroic dye (D7)]
In the synthesis of the 4-nitro-4′-hydroxyazobenzene intermediate in the synthesis of the dichroic dye (D1), 4-nitroaniline is changed to 2-methyl-4-nitroaniline, and the trisazo intermediate 4- [ 4- [4- (4-Hydroxyphenylazo) phenylazo] naphthylazo] -N, N-diethylaniline N, N-diethylaniline was changed to N, N-diethyl-o-toluidine in the same manner as described below. Thus, 0.3 g of a trisazo-based polymerizable dichroic dye (D7) represented by the structural formula was obtained.

  The obtained polymerizable dichroic dye (D7) had an HPLC purity of 99.1% and an absorption maximum wavelength of 570 nm. Further, the crystal changed to an isotropic phase at 144 ° C. when the temperature was raised, but changed from the isotropic phase to the liquid crystal phase at 120 ° C. when the temperature was lowered, and showed liquid crystallinity up to room temperature. The molecular length of the compound calculated in the same manner as described above (the distance from the leftmost carbon atom of the leftmost benzene ring to the rightmost carbon atom of the rightmost benzene ring) was 2.15 nm.

<Preparation of polymerizable liquid crystal compound (A1) and polymerizable liquid crystal composition (B)>
As the polymerizable liquid crystal compound (A1) having no “negative dispersion” characteristics, “Palio Color LC242” manufactured by BASF was used. Further, as the polymerizable liquid crystal composition (B) having “negative dispersion” characteristics, 17.6 parts by weight of a rod-like liquid crystal compound (21) represented by the following formula (22) and a compound having two or more kinds of mesogenic groups (22 ) Was mixed at a ratio of 2 parts by weight to prepare a polymerizable liquid crystal composition (B). The rod-like liquid crystal compound (21) and the compound (22) having two or more kinds of mesogenic groups were produced by the method described in JP-A No. 2002-267838.

(Reference Example 1)
The above-mentioned dichroic dye (D1) is added to the polymerizable liquid crystal compound (A1) having no “negative dispersion” characteristic at a ratio of 1 part by weight relative to 100 parts by weight of the total amount, and a polymerization initiator is further added. (Trade name “LUCIRIN TPO” manufactured by BASF, solid at room temperature (25 ° C.)) is 4.0 with respect to 100 parts by weight of the total amount of the polymerizable liquid crystal compound (A1) and the dichroic dye (D1). The 1st mixture (solid) added in the ratio used as a weight part was obtained. Next, the first mixture is dissolved in a chlorobenzene solvent, the insoluble matter is filtered through a polytetrafluoroethylene filter having a pore size of 0.45 μm, and the polymerizable liquid crystal compound (A1), dichroic dye ( A mixed solution (second mixture) containing D1), a polymerization initiator and a solvent was obtained. In the production of such a second mixture, the content of the solvent in the second mixture is 80% by weight, and the total amount of the liquid crystal compound, the dichroic dye and the polymerization initiator is 20% by weight. % Of the solvent was used.

  Next, a 38 μm thick polyethylene naphthalate film (manufactured by Teijin Limited) was cut into a 15 cm square, and a 5 wt% solution of alkyl-modified polyvinyl alcohol (PVA: manufactured by Kuraray Co., Ltd., MP-203) (the solvent was water). And a mixture solvent of isopropyl alcohol in a weight ratio of 1: 1) was applied by spin coating, dried on a hot plate at 50 ° C. for 30 minutes, and then heated in an oven at 120 ° C. for 10 minutes. Subsequently, it was rubbed with a rayon rubbing cloth. The film thickness of the obtained PVA layer was 1.2 μm. The peripheral speed ratio during rubbing (moving speed of rubbing cloth / moving speed of substrate film) was 4. A mixed solution (second mixture) containing a polymerizable liquid crystal compound, a dichroic dye, a polymerization initiator, and a solvent is applied to the alignment substrate thus obtained by a spin coating method to form a coating film (wet film). (Thickness: 5 μm) was formed to obtain a laminate of the coating film and the alignment substrate.

  Next, the laminate of the coating film and the alignment substrate was left to stand for 4 minutes under the conditions of pressure: 1013 hPa and temperature: 80 ° C., thereby removing the solvent from the coating film by drying (solvent removal step). In addition, the solvent was removed from the entire surface of the coating film after 4 minutes had passed since the coating on the alignment substrate was completed.

Next, with respect to the coating film after being dried by the solvent removal step, an ultraviolet light (however, 365 nm) is used by using a high-pressure mercury lamp with an illuminance of 15 mW / cm ^{2 so} that the integrated irradiation amount becomes 200 mJ / cm ^2. The polymerizable liquid crystal compound is polymerized (cured) to fix the alignment state, and a liquid crystal film in which the alignment state is fixed is laminated on the alignment substrate. A laminate (a laminate of a liquid crystal film and an alignment substrate) was obtained.

  Since the polyethylene naphthalate film used as the substrate has a large birefringence and is not preferable as an optical film, the optically anisotropic layer on the obtained alignment substrate is subjected to triacetylcellulose (TAC) via an ultraviolet curable adhesive. ) Transferred to film. That is, on the cured liquid crystal film layer on the polyethylene naphthalate film, an adhesive is applied to a thickness of 5 μm, laminated with a TAC film, and irradiated with ultraviolet rays from the TAC film side to cure the adhesive. After that, the alignment substrate was peeled off.

  When the optical film (liquid crystal film / adhesive layer / TAC film) obtained as described above was observed under a polarizing microscope, it was found that there was no disclination and the monodomain was uniformly oriented.

  Moreover, the polarization absorption spectrum of the obtained optical film (liquid crystal film / adhesive layer / TAC film) was measured using a spectroscopic spectrum (V-570) manufactured by JASCO Corporation and an adapter capable of inserting a polarizing prism in the optical path. did. Ae (λ) is the polarization absorption spectrum measured with the easy transmission axis of the polarizing prism inserted in the optical path parallel to the slow axis of the liquid crystal film, and the polarization absorption spectrum measured with the easy transmission axis and the slow axis perpendicular. Ao (λ) was set. Each unit is absorbance (OD).

  Further, an optical film was prepared in the same manner as described above except that the dichroic dye (D1) was not added to the polymerizable liquid crystal compound (A1), and the polarization absorption spectrum Ae0 parallel to the slow axis was obtained in the same manner as described above. Ao0 (λ) was measured for (λ) and the polarization absorption spectrum perpendicular to the slow axis.

Each polarization absorption spectrum measured is expressed by the following formula (1):
S = (DR-1) / (DR + 2) (1)
(In the formula (1), DR represents the following formula (2):
Represents. And the absorption dichroic ratio (DR) and the order parameter (S) were calculated. The absorption dichroic ratio was 5.7 and the order parameter was 0.61.

(Reference Example 2)
The dichroic dye (D1) was added at a ratio of 1.0 part by weight with respect to 100 parts by weight of the total amount of the polymerizable liquid crystal composition (B), and a polymerization initiator (trade name “manufactured by BASF” Irgacure 651 ”, solid at room temperature (25 ° C.), is added at a ratio of 1.0 part by weight to 100 parts by weight of the total amount of the polymerizable liquid crystal compound (B) and the dichroic dye, A third mixture (solid) obtained by mixing the polymerizable liquid crystal compound (B), the dichroic dye D1 and the polymerization initiator was obtained.

  Next, the third mixture is dissolved in methyl ethyl ketone (solvent), the insoluble matter is filtered through a polytetrafluoroethylene filter having a pore size of 0.45 μm, and the polymerizable liquid crystal compound (B), dichroic dye A mixed solution (fourth mixture) containing (D1), a polymerization initiator, and a solvent was obtained. In producing the fourth mixture, the content of the solvent in the fourth mixture is 80% by weight, and the polymerizable liquid crystal compound (B), the dichroic dye (D1), and the polymerization are mixed. The solvent was used so that the total amount with the initiator was 20% by weight.

  Reference Example 1 except that the above-mentioned fourth mixed solution was used and the solvent removal step was performed by leaving it for 2 minutes under the conditions of pressure: 1013 hPa and temperature: room temperature (25 ° C.) Similarly, an optical film (optical anisotropic layer / adhesive layer / TAC film) was obtained.

  When the obtained optical film (liquid crystal film / adhesive layer / TAC film) was observed under a polarizing microscope, it was found that there was no disclination and uniform orientation of the monodomain. In addition, the wavelength dispersion characteristic of retardation (Δnd) in the in-plane direction of the laminate of the TAC film and the liquid crystal layer and the TAC film alone was measured using a trade name “Axoscan” manufactured by Axometrix, and the liquid crystal was calculated by subtracting both. The birefringence wavelength dispersion characteristics of the film layer were measured. The birefringence wavelength dispersion characteristic of the liquid crystal film layer was as shown in FIG. Further, in the obtained liquid crystal film, Δn · d (500) / Δn · d (550) = 0.898 and Δn · d (580) / Δn · d (550) = 1.49. Further, Δn · d at 550 nm was 141.6 nm.

  Further, an optical film (optically anisotropic layer / adhesive layer / TAC film) was produced in the same manner as in Reference Example 1 except that the dichroic dye (D1) was removed from the fourth mixture, and Reference Example 1 was measured, and the absorption dichroic ratio (DR) and the order parameter (S) were calculated from the above formulas (1) and (2). 3 and the order parameter was 0.52. Based on the above results, the same dichroic dye D1 was added to a polymer having a “negative dispersion” characteristic as compared with Reference Example 1 in which a normal dispersion liquid crystal having no “negative dispersion” characteristic was added. In Example 2, it was found that the decrease in order parameter was suppressed to 0.86 times.

Example 1
In Reference Example 2, an optical film was produced in the same manner as in Reference Example 2 except that the addition amount of the dichroic dye (D1) was changed to 0.065 parts by weight.
In the obtained optical film, Δn · d (500) / Δn · d (550) = 0.978 and Δn · d (580) / Δn · d (550) = 1.010. Further, Δn · d at 550 nm was 140.9 nm.
Further, an optical film (an optically anisotropic layer / adhesive layer / TAC film) was produced in the same manner as in Reference Example 2 except that the dichroic dye (D2) was removed. The respective polarized absorption spectra were measured, and the absorption dichroic ratio (DR) and the order parameter (S) were calculated from the above formulas (1) and (2). The absorption dichroic ratio (DR) and the order parameter (S ) Was calculated, the absorption dichroic ratio was 4.3, and the order parameter was 0.52.
The obtained optical film is bonded to a commercially available polarizing plate (SRW062 manufactured by Sumitomo Chemical Co., Ltd.) via an acrylic adhesive so that the absorption axis of the polarizing plate and the optical axis of the optical film are 45 degrees. The board was produced and it affixed on the transparent glass substrate of the organic EL element of a commercially available organic EL display via the acrylic adhesive, and produced the organic EL display apparatus. As a result, it was found that an organic EL display device that exhibits a significant effect of preventing reflection of external light and has excellent visibility as compared with the case where no circularly polarizing plate is provided. When the front reflectance was evaluated, it was 0.85%. Further, the emission spectrum of this organic EL display device is a graph shown in FIG. 13, and the transmittance is reduced by 2.1% compared to the case where an optical film produced in the same manner except that no dye is added is bonded. It was confirmed that

(Example 2)
In Example 1, the optical film was produced like Example 1 except having changed the said dichroic dye (D1) into the dichroic dye (D2), and having changed the addition amount into 0.043 weight part. . When the birefringent wavelength dispersion characteristic of the liquid crystal film layer was measured, Δn · d at 550 nm was 140.5 nm, Δn · d (500) / Δn · d (550) = 0.980, Δn · d ( 580) / Δn · d (550) = 1.010. Table 2 summarizes the optical property results.

  Further, when the absorption dichroic ratio (DR) and the order parameter (S) were calculated in the same manner as in Example 1 except that the dichroic dye (D2) was used, the absorption dichroic ratio was 4.4. Yes, the order parameter was 0.53. Further, an organic EL display device was produced in the same manner as in Example 1 except that the optical film obtained above was used. When the front reflectance and transmittance decrease were evaluated in the same manner as in Example 1, the front reflectance was 0.85% and the transmittance decrease was 1.9%.

(Example 3)
In Example 1, the optical film was produced like Example 1 except having changed the said dichroic dye (D1) into the dichroic dye (D3), and having changed the addition amount into 0.062 weight part. . When the birefringent wavelength dispersion characteristic of the liquid crystal film layer was measured, Δn · d at 550 nm was 140.8 nm, Δn · d (500) / Δn · d (550) = 0.978, Δn · d ( 580) / Δn · d (550) = 1.003. Table 2 summarizes the optical property results.

  Further, when the absorption dichroic ratio (DR) and the order parameter (S) were calculated in the same manner as in Example 1 except that the dichroic dye (D3) was used, the absorption dichroic ratio was 6.5. Yes, the order parameter was 0.65. Further, an organic EL display device was produced in the same manner as in Example 1 except that the optical film obtained above was used. When the front reflectance and transmittance decrease were evaluated in the same manner as in Example 1, the front reflectance was 0.85% and the transmittance decrease was 1.9%.

Example 4
In Example 1, the optical film was produced like Example 1 except having changed the said dichroic dye (D1) into the dichroic dye (D7), and having changed the addition amount into 0.06 weight part. . When the birefringent wavelength dispersion characteristic of the liquid crystal film layer was measured, Δn · d at 550 nm was 140.6 nm, Δn · d (500) / Δn · d (550) = 0.799, Δn · d ( 580) / Δn · d (550) = 1.003. Table 2 summarizes the optical property results.

  Further, when the absorption dichroic ratio (DR) and the order parameter (S) were calculated in the same manner as in Example 1 except that the dichroic dye (D7) was used, the absorption dichroic ratio was 3.6. Yes, the order parameter was 0.46. Further, an organic EL display device was produced in the same manner as in Example 1 except that the optical film obtained above was used. When the front reflectance and transmittance decrease were evaluated in the same manner as in Example 1, the front reflectance was 0.85% and the transmittance decrease was 2.2%.

(Comparative Example 1)
In Example 1, the optical film was produced like Example 1 except having changed the said dichroic dye (D1) into the dichroic dye (D4), and having changed the addition amount into 0.062 weight part. . When the birefringent wavelength dispersion characteristic of the liquid crystal film layer was measured, Δn · d at 550 nm was 140.7 nm, Δn · d (500) / Δn · d (550) = 0.799, Δn · d ( 580) / Δn · d (550) = 1.014. Table 2 summarizes the optical property results.

  Further, when the absorption dichroic ratio (DR) and the order parameter (S) were calculated in the same manner as in Example 1 except that the dichroic dye (D4) was used, the absorption dichroic ratio was 1.8. Yes, the order parameter was 0.21. Further, an organic EL display device was produced in the same manner as in Example 1 except that the optical film obtained above was used. When the front reflectance and transmittance decrease were evaluated in the same manner as in Example 2, the front reflectance was 0.85% and the transmittance decrease was 2.8%.

(Comparative Example 2)
In Example 1, the optical film was produced like Example 1 except having changed the said dichroic dye (D1) into the dichroic dye (D5), and having changed addition amount into 0.100 weight part. . When the birefringent wavelength dispersion characteristic of the liquid crystal film layer was measured, Δn · d at 550 nm was 140.5 nm, Δn · d (500) / Δn · d (550) = 0.980, Δn · d ( 580) / Δn · d (550) = 1.010. Table 2 summarizes the optical property results.

  Further, when the absorption dichroic ratio (DR) and the order parameter (S) were calculated in the same manner as in Example 1 except that the dichroic dye (D5) was used, the absorption dichroic ratio was 1.9. Yes, the order parameter was 0.23. Further, an organic EL display device was produced in the same manner as in Example 1 except that the optical film obtained above was used. When the front reflectance and transmittance decrease were evaluated in the same manner as in Example 1, the front reflectance was 0.85%, and the transmittance decrease was 3.3%.

(Comparative Example 3)
In Example 1, the optical film was produced like Example 1 except having changed the said dichroic dye (D1) into the dichroic dye (D6), and having changed the addition amount into 0.204 weight part. . When the birefringent wavelength dispersion characteristic of the liquid crystal film layer was measured, Δn · d at 550 nm was 141.2 nm, Δn · d (500) / Δn · d (550) = 0.980, Δn · d ( 580) / Δn · d (550) = 1.010. Table 2 summarizes the optical property results.

  Moreover, when the absorption dichroic ratio (DR) and the order parameter (S) were calculated in the same manner as in Example 1 except that the dichroic dye (D6) was used, the absorption dichroic ratio was 2.1. Yes, the order parameter was 0.27. Further, an organic EL display device was produced in the same manner as in Example 1 except that the optical film obtained above was used. When the front reflectance and transmittance decrease were evaluated in the same manner as in Example 1, the front reflectance was 0.85% and the transmittance decrease was 2.9%.

(Comparative Example 4)
In Example 1, the dichroic dye (D1) in the mixed solution (fourth mixture) containing the polymerizable liquid crystal compound (B), the dichroic dye (D1), the polymerization initiator and the solvent was not added. An optical film was produced in the same manner as in Example 1 except that. When the birefringent wavelength dispersion characteristic of the liquid crystal film layer was measured, Δn · d at 550 nm was 143.0 nm, Δn · d (500) / Δn · d (550) = 0.981, Δn · d ( 580) / Δn · d (550) = 1.09. Table 2 summarizes the optical property results.

  Further, an organic EL display device was produced in the same manner as in Example 1 except that the optical film obtained above was used. When the front reflectance and transmittance decrease were evaluated in the same manner as in Example 1, the front reflectance was 1.18% and the transmittance decrease was 0.0%.

1: Rod-shaped molecule 2: Polymer film 3: Discotic molecule

Claims (9)

A composition comprising a polymerizable liquid crystal composition having a “negative dispersion” characteristic in which birefringence Δn becomes larger as the measurement wavelength is longer in at least a part of the wavelength region of the visible light region, and a dichroic dye. A retardation plate comprising a film comprising a polymer obtained by polymerizing
Containing 0.03 to 0.8 parts by weight of the dichroic dye with respect to 100 parts by weight of the polymerizable liquid crystal composition;
The retardation plate represented by the following formula (1), wherein the order parameter (S) of the dichroic dye in the polymer is in a range of 0.4 ≦ S ≦ 1.0.
S = (DR-1) / (DR + 2) (1)
(In the formula (1), DR is an absorption dichroic ratio of the dichroic dye represented by the following formula (2).)
(In the formula (2), λ represents the wavelength (nm) of light in vacuum,
A _e (λ) represents a polarization absorption spectrum parallel to the slow axis in the polymer,
A _o (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the polymer,
A _e0 (λ) represents a polarization absorption spectrum parallel to the slow axis in a polymer obtained by polymerizing the polymerizable liquid crystal composition excluding the dichroic dye,
A _o0 (λ) represents a polarized light absorption spectrum perpendicular to the slow axis in a polymer obtained by polymerizing the polymerizable liquid crystal composition excluding the dichroic dye. )   The both of the extraordinary ray refractive index ne and the birefringence Δn have a “negative dispersion” characteristic that increases as the measurement wavelength increases in at least a part of the wavelength region of the visible light region. Phase difference plate.   The phase difference plate according to claim 1, wherein the orientation of the polymer is in a parallel orientation state.   The retardation plate according to any one of claims 1 to 3, wherein the dichroic dye is a rod-like molecule, and a molecular length in a major axis direction is 2 nm to 10 nm.   The phase difference plate according to any one of claims 1 to 4, wherein an absorption maximum wavelength of the dichroic dye is in a measurement wavelength region of 400 to 780 nm.   The retardation plate according to claim 1, wherein an absorption maximum wavelength of the dichroic dye is different from an absorption maximum wavelength of an emission spectrum of the image display device.   The elliptically polarizing plate provided with the phase difference plate and polarizing plate as described in any one of Claims 1-6.   An image display device comprising the elliptically polarizing plate according to claim 7.   The image display device according to claim 8, which is a liquid crystal display device or an organic electroluminescence display device.