JP6392257B2 - Retardation plate, laminated polarizing plate using retardation plate, and display device using retardation plate - Google Patents

Description

  The present invention relates to a retardation plate, a laminated polarizing plate using the retardation plate, and an image display device, a liquid crystal display device, and an organic electroluminescence (EL) display device using the retardation plate.

  The phase difference plate is an optical element used to obtain polarized light (linearly polarized light, circularly polarized light, elliptically polarized light), and is used for color compensation and viewing angle improving films for liquid crystal display devices, linear polarizers and 1/4 wavelength. In many applications, such as the use of anti-reflection films for organic EL display devices combined with plates, and the use of reflective polarizing plates that reflect either right-handed or left-handed circularly polarized light consisting of cholesteric liquid crystals, etc. Used. Retardation plates are thin films of inorganic materials (calcite, mica, quartz), films obtained by stretching polymer films with high intrinsic birefringence, and films in which a rod-shaped or disk-shaped liquid crystal composition is oriented and fixed in the liquid crystal state. Is used.

  As the retardation plate, a ¼ 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 typical. The quarter wavelength 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 degrees.

  The retardation plate is usually designed so as to exhibit a necessary optical function with respect to light of a specific wavelength (monochromatic light). However, the above-described color compensation film for liquid crystal display devices and organic EL displays are used. A quarter-wave plate used as an antireflection film for an apparatus has an action of converting linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light at a measurement wavelength (λ) of 400 to 700 nm in the visible light region. There is a need. If this is to be realized with a single retardation plate, the ideal retardation plate has a phase difference of ¼ wavelength (λ / 4) of the measurement wavelength at a measurement wavelength of 400 to 700 nm.

  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, a dispersion characteristic that is larger as the measurement wavelength is shorter and becomes smaller as the wavelength is longer is defined as “positive dispersion”, and a dispersion characteristic that is smaller as the measurement wavelength is shorter and becomes greater as the longer wavelength 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, and it has a “positive dispersion” characteristic made of a general polymer film. If the phase difference plate is used for white light in which light in the visible light range is mixed, a distribution of polarization states at each wavelength is generated, and colored polarized light is generated.

Patent Documents 1 and 2 each disclose a retardation plate obtained by laminating two polymer films having optical anisotropy. The retardation plate described in Patent Document 1 includes a quarter-wave plate in which the phase difference of birefringent light is ¼ wavelength, and a ½ wavelength plate in which the phase difference of birefringent light is ½ wavelength. , And pasted together with their optical axes crossed. The phase difference plate described in Patent Document 2 is formed by laminating at least two phase difference plates having an optical phase difference value of 160 to 320 nm so that their slow axes are not parallel or orthogonal to each other. In Patent Document 3, the slow axis of the birefringent medium in which the relationship of the wavelength dispersion value α (α = Δn (450 nm) / Δn (650 nm)) of the birefringence index Δn is αA <αB is laminated in an orthogonal direction. Laminated type in which at least one of the birefringent media is composed of a liquid crystal compound in a molecular orientation state in which the orientation is homogeneous, the phase difference R of each birefringent media is R _A > R _B , and the wavelength dispersion value α is smaller than 1. A phase difference plate is disclosed. Specifically, the retardation plate described in any of the publications is composed of a laminate of two birefringent media.

  By adopting the methods described in the above publications, a quarter wavelength plate can be achieved in a wide wavelength region. However, in the manufacture of the phase difference plate described in each of Patent Document 1 and Patent Document 2, in order to adjust the optical orientation (optical axis and slow axis) of the two polymer films, a complicated manufacturing process is required. Need. 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. And in invention of each gazette of patent document 1 and patent document 2, the optical direction of two polymer films is set to the angle which is neither parallel nor orthogonal. Therefore, in order to manufacture the retardation plate described in each of Patent Document 1 and Patent Document 2, it is necessary to cut two types of polymer films at a predetermined angle and bond the obtained chips together. If a phase difference plate is manufactured by bonding chips, the process is complicated, the quality is likely to deteriorate due to axial misalignment, the yield decreases, the cost increases, and deterioration due to contamination is likely to occur. In addition, it is difficult to strictly adjust the optical retardation value in a polymer film.

  The cause of birefringence wavelength dispersion of an anisotropic rod-like molecule is the two refractive indices ne and no (ne is an “abnormal refractive index” in a direction parallel to the long molecular axis, and no is “Ordinary ray refractive index” in the direction perpendicular to the long molecular axis. FIG. 2 shows the relationship of the refractive index of the rod-like molecule 1 in the polymer film 2) varies at different speeds depending on the wavelength. As shown, due to the fact that ne changes more rapidly than no toward the shorter wavelength side of the visible wavelength spectrum. 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 refractive index in the major axis direction (abnormal light refractive index ne) is in the visible light region. It has absorption in the near ultraviolet region and changes rapidly toward the short wavelength side of the visible wavelength spectrum, whereas the refractive index in the minor axis direction (ordinary ray refractive index) has a comparatively gentle curve. To do.

One way to achieve higher dispersion of the “positive dispersion” property of birefringence is to design a molecule in which the positive dispersion of ne is increased and the positive dispersion of no is decreased, as shown in FIG. . This method is possible by designing a rod-like molecular structure having absorption in the ultraviolet region closer to the visible light region, or by mixing a dye having absorption in the ultraviolet region. 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. In the retardation plate described in Patent Document 4, by adding a dye having absorption in the ultraviolet region, the dye is oriented in the major axis direction of the rod-like molecule, and the short wavelength region is more than the original extraordinary ray refractive index. It is clearly shown that it is designed to change sharply, that is, the “positive dispersion” property of the phase difference can be made higher. However, as a method for imparting the “negative dispersion” property, which is the object of the present invention, only a method in which two polymer films to which a pigment is added is superposed perpendicularly is described.
On the other hand, as a method of obtaining a “negative dispersion” characteristic in which birefringence increases as the wavelength increases, a molecule in which the positive dispersion of no is increased and the positive dispersion of ne is decreased is designed in the opposite direction to FIG. I can do it.

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

  Patent Document 5 discloses a retardation obtained by uniaxially stretching 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. A retardation plate having a “negative dispersion” characteristic with a single film is disclosed. The retardation film described in Patent Document 5 will be described with a schematic diagram as shown in FIG. 5 and a birefringence wavelength dispersion characteristic graph as shown in FIG. In an organic polymer having “positive birefringence” (denoted by rod-like molecule 1 in FIG. 5), birefringence Δn1 (= ne1−no1)> 0, where an extraordinary ray refractive index is ne1 and an ordinary ray refractive index is no1. It becomes. In an organic polymer having “negative birefringence” (denoted by the discotic molecule 3 in FIG. 5), when the extraordinary ray refractive index is ne2 and the ordinary ray refractive index is no2, Δn2 (= ne2−no2) <0. Become. 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. When the wavelength dispersion characteristic D2 of the organic polymer having “birefringence” is designed to be larger than the wavelength dispersion characteristic D1 of the organic polymer having “positive birefringence” (that is, D2> 1), 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.

  Patent Document 6 discloses a liquid crystal film made of a rod-like liquid crystal compound as a retardation plate which is a thin film and becomes larger as the measurement wavelength becomes longer. The retardation plate described in Patent Document 6 homogenously aligns a liquid crystal composition containing a compound having two or more kinds of mesogenic groups and a rod-like liquid crystal compound, 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, the method of combining a compound composed of a positive birefringent material and a negative birefringent material having different birefringence wavelength dispersion characteristics described in Patent Document 5 and Patent Document 6 is a broadband with a measurement wavelength of 400 to 700 nm in the visible light region. In such a region, it is difficult to obtain a characteristic in which the phase difference becomes a quarter wavelength of the measurement wavelength. Generally, as shown in FIG. 7, 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 approach the ideal chromatic dispersion curve in the wide-band region of the measurement wavelength 400 to 700 nm that is the visible light region, the curve on the short wavelength side is maintained in a state close to the ideal straight line, and another method is used. An attempt to bring the wavelength curve closer to the ideal straight line is necessary.
In addition, the circularly polarizing plate described above achieves a quarter wavelength plate in a wide wavelength region, so that near-ideal circularly polarized light can be obtained in light incident from the normal direction of the circularly polarizing plate. Light incident from the direction is converted into elliptically polarized light that deviates significantly from circularly polarized light, narrowing the viewing angle of the display in the liquid crystal display device, or light leakage in an oblique direction in the antireflection plate in the organic EL display device May occur.
Patent Document 7 discloses a circularly polarizing plate in which a birefringent material of NZ <0 is provided between a polarizer and a quarter wavelength plate. Here, NZ is NZ = (nx-nz) / nx-ny) (where nx and ny represent the in-plane main refractive index with respect to light having a wavelength of 550 nm, and nx ≧ ny is satisfied. It represents the main refractive index in the thickness direction for light of 550 nm. The circularly polarizing plate described in Patent Document 7 compensates for the viewing angle dependency of the phase difference by providing a birefringent body with NZ <0, and improves the viewing angle characteristics of the circularly polarizing plate. There are adverse effects such as cost increase and thickness increase by using a special material of 0.
Patent Documents 8 and 9 disclose a circularly polarizing plate made of a liquid crystal film in which a polarizing plate and a nematic hybrid alignment structure having a phase difference of approximately a quarter wavelength are fixed. It has been proposed as a method of widening the viewing angle of a display in a transmissive or reflective liquid crystal display device by a circularly polarizing plate comprising a quarter wavelength plate having a nematic hybrid alignment structure and a polarizing plate. In order to achieve a four-wave plate, a combination with a half-wave plate made of a polymer stretched film is necessary, and an increase in cost and thickness is inevitable.

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 JP 2005-326818 A JP 2002-31717 A JP 2000-321576 A

  The object of the present invention has been made in view of the above-described present situation, while minimizing a decrease in transmittance, a retardation plate having desired birefringence wavelength dispersion characteristics, a laminated polarizing plate using the retardation plate, And a wide viewing angle display device using a retardation plate.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have 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. A retardation plate comprising a polymerizable liquid crystal composition and at least one dichroic dye, and comprising a liquid crystal film in which a liquid crystal compound is nematic hybrid aligned. I learned that the problem can be solved. The present invention has been completed based on such findings.

[1] A phase difference plate 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,
A retardation film comprising a polymerizable liquid crystal composition and at least one dichroic dye, and comprising a liquid crystal film in which a liquid crystal compound is nematic hybrid aligned.
[2] Retardation in the normal direction of the retardation plate is Δna · da,
Retardation in the normal direction of a retardation film composed of a liquid crystal film obtained by removing the dichroic dye from the liquid crystal film is Δnb · db,
When the following formula (1):
Δna · da (580) / Δna · da (550) −Δnb · db (580) / Δnb · db (550)> 0 (1)
(Here, the retardation is represented by the product of birefringence Δn and the thickness d of the retardation plate, and Δna · da (580) and Δna · da (580) are retardations of each retardation plate at a wavelength of 580 nm). Δna · da (550) and Δna · da (550) are retardations of each phase difference plate at a wavelength of 550 nm.)
The retardation plate according to [1], wherein
[3] The retardation plate according to [1] or [2], wherein the liquid crystal compound is formed of a liquid crystal film with twisted nematic hybrid alignment.
[4] In the liquid crystal film, a mixture containing a polymerizable liquid crystal composition and at least one dichroic dye is nematic hybrid aligned in a liquid crystal state, and the alignment is fixed by a crosslinking reaction by light or heat. The retardation plate according to [1] or [2].
[5] The liquid crystal film has a twisted nematic hybrid alignment in a liquid crystal state of a mixture containing a polymerizable liquid crystal composition and at least one dichroic dye, and the alignment is fixed by a crosslinking reaction by light or heat. The retardation plate according to [3], wherein
[6] The retardation ratio in the normal direction of the retardation plate at a specific wavelength is expressed by the following mathematical formulas (2) and (3):
0.80 <Δn · d (500) / Δn · d (550) <1.00 (1)
1.00 <Δn · d (600) / Δn · d (550) <1.15 (2)
(Here, retardation is represented by the product of birefringence Δn and the film thickness d of the retardation plate, and Δn · d (500), Δn · d (550), and Δn · d (600) are respectively wavelengths. Retardation of retardation plate at 500 nm, 550 nm, and 600 nm.)
The retardation film according to any one of [1] to [5], wherein
[7] The phase difference plate according to any one of [1] to [6], wherein the maximum absorption wavelength of the dichroic dye is in a measurement wavelength region of 380 to 780 nm.
[8] The retardation plate according to any one of [1] to [7], wherein the maximum wavelength of the emission spectrum of the image display device is different from the maximum absorption wavelength of the dichroic dye.
[9] The retardation plate according to any one of [1] to [8], wherein the liquid crystal film has an average tilt angle of liquid crystal molecules of 5 to 45 degrees.
[10] The retardation plate according to any one of [1] to [9], wherein a twist angle in a film plane of liquid crystal molecules of the liquid crystal film is 0 to 70 degrees.
[11] A laminated polarizing plate comprising the retardation plate according to any one of [1] to [10] and a polarizer.
[12] A display device comprising the retardation plate according to any one of [1] to [10].

  According to the present invention, in the retardation plate having a “negative dispersion” characteristic in which the birefringence Δn is increased as the measurement wavelength is longer in at least a part of the wavelength region of the visible light region, the polymerizable liquid crystal composition, There can be provided a phase difference plate comprising a liquid crystal film comprising at least one kind of dichroic dye and having a liquid crystal compound nematic hybrid aligned. A retardation plate having such a liquid crystal alignment structure and birefringence wavelength dispersibility and having a phase difference of 1/4 wavelength at a measurement wavelength of 550 nm makes circularly polarized light linearly polarized in a wide wavelength region in the front and oblique directions. Furthermore, since it functions as a phase difference plate that converts linearly polarized light into circularly polarized light, when used in a liquid crystal display device, display characteristics such as brightness and contrast ratio are improved in the front and oblique directions, and the organic electroluminescence display device is improved. If used, the high prevention performance against specular reflection is greatly improved at a wide viewing angle.

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 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 and the ordinary ray refractive index no of the rod-shaped molecule | numerator which has anisotropy. 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 polymer. 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 three colors of the organic electroluminescence display device are lit simultaneously and three colors are lit simultaneously to display white. It is a conceptual diagram of the orientation structure of a nematic hybrid liquid crystal film. It is a conceptual diagram for demonstrating the tilt angle and twist angle of a liquid crystal molecule. It is a figure which shows the wavelength dispersion characteristic of birefringence (DELTA) n of the liquid crystal film produced in Example 1, Example 2, Example 3, the comparative example 1, and the comparative example 3. FIG. It is a measurement result of the apparent retardation value measured by inclining the liquid crystal film produced in Example 1 along the alignment direction of a liquid crystal. 2 is a diagram illustrating a layer configuration of circularly polarizing plates manufactured in Example 1, Comparative Example 2, and Comparative Example 3. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in Example 1 is mounted in an organic electroluminescence display. 6 is a diagram showing a layer structure of a circularly polarizing plate produced in Example 2. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in Example 2 is mounted in an organic electroluminescence display. It is a measurement result of the apparent retardation value measured by inclining the liquid crystal film produced in Example 3 along the alignment direction of a liquid crystal. 6 is a diagram showing a layer structure of a circularly polarizing plate produced in Example 2. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in Example 2 is mounted in an organic electroluminescence display. 4 is a diagram illustrating a layer configuration of a circularly polarizing plate manufactured in Example 3. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in Example 3 is mounted in an organic electroluminescence display. 6 is a diagram showing a layer configuration of a circularly polarizing plate manufactured in Comparative Example 1. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in the comparative example 1 is mounted in an organic electroluminescence display. It is a figure which shows the wavelength dispersion characteristic of birefringence (DELTA) n of the liquid crystal film produced in the comparative example 1. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all the directions when the circularly-polarizing plate produced in the comparative example 2 is mounted in an organic EL display apparatus. It is a figure which shows the wavelength dispersion characteristic of birefringence (DELTA) n of the liquid crystal film produced in the comparative example 3. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in the comparative example 3 is mounted in an organic electroluminescence display.

<Phase difference plate>
The retardation plate of the present invention is a retardation plate 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 liquid crystal film comprising a composition and at least one dichroic dye and having a liquid crystal compound nematic hybrid aligned.
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.

First, the refractive index wavelength dispersion characteristic of the organic polymer will be described with reference to FIG.
Hereinafter, the refractive index is described as a complex number N = n−ik. Here, n is a real part of N and is equal to what is usually called “refractive index”. k (imaginary part of N) is expressed as k = αλ / (4π) as a function of wavelength α (λ) and is 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”. Both the molecular copolymer and the mixture are made of a material having an extraordinary ray refractive index ne and an ordinary ray refractive index no having “positive dispersion” characteristics.
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” property, in a wavelength region having a visible light region, The design philosophy is fundamental in that the extraordinary ray refractive index ne has a “negative dispersion” characteristic and, accordingly, the birefringence Δn becomes a phase difference plate having a “negative dispersion” characteristic in the visible light region. Different.

The retardation plate of the present invention is a retardation plate in which birefringence Δn has a “negative dispersion” characteristic in at least a part of the wavelength region of the visible light region. A method for designing birefringence Δn having “negative dispersion” characteristics, which is a feature of the retardation plate of the present invention, will be described.
It is formed by uniaxially stretching 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 described above. In the case of a liquid crystal film comprising a retardation film or a liquid crystal composition comprising a compound having two or more kinds of mesogenic groups exemplified in Patent Document 6 and a rod-like liquid crystal compound, “positive birefringence” as shown in FIG. In addition, a retardation plate having “negative dispersion” characteristics can be obtained. 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 curve in the wide-band region of the measurement wavelength 400 to 700 nm that is the visible light region, the curve on the short wavelength side is maintained in a state close to the ideal straight line, and another method is used. An attempt to bring the wavelength curve closer to the ideal straight line is necessary. In view of the above situation, attention was paid to the “negative dispersion” characteristic resulting from 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 +.

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. In this organic polymer, by adding a dye having high dichroism having an absorption spectrum having a maximum absorption wavelength at 580 nm as shown in FIG. 11, in the wavelength region of 550 to 650 nm which is near the absorption wavelength, A retardation plate having the characteristic that the light refractive index ne is “negative dispersion” is obtained. Here, high dichroism means that there is a large difference in absorption characteristics between the ne direction and the no direction. FIG. 12 shows the birefringence wavelength dispersion characteristics of a retardation plate composed of an organic polymer before and after the addition of the dichroic dye. By adding a dichroic dye, a retardation plate having birefringence having “negative dispersion” in a wavelength region of 550 to 650 nm can be obtained.
From the above, by adding a dichroic dye having an anomalous dispersion region to a liquid crystal compound whose birefringence has a “positive dispersion” characteristic, in the entire wavelength region of visible light, which is the object of the present invention, A phase difference plate having “negative dispersion” characteristics with refraction closer to ideal is obtained.
In addition, in the case of using an organic polymer whose birefringence has a “negative dispersion” characteristic, the “negative dispersion” characteristic in the birefringence may be inferior in a long wavelength region, and two colors having an anomalous dispersion region. By adding a functional dye, a long wavelength region can be improved, and a film having a “negative dispersion” characteristic in which birefringence is closer to ideal in the entire wavelength region of visible light, which is also an object of the present invention, can be obtained.

  The retardation plate of the present invention has a “negative dispersion” characteristic in which the extraordinary ray refractive index ne becomes larger as the measurement wavelength is longer in at least a part of the wavelength region of the visible light region. In the visible light region, the retardation plate has a “negative dispersion” characteristic that increases as the measurement wavelength increases. The visible light region generally represents a region of 380 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, ne is preferably as long as possible over the entire wavelength of visible light. 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 consideration of human specific visibility characteristics, if a “negative dispersion” characteristic can be obtained within a wavelength range of 550 to 600 nm, a sufficiently desired characteristic can be obtained.

  The retardation plate of the present invention is a retardation plate characterized in that the birefringence Δn has a “negative dispersion” characteristic that becomes larger as the measurement wavelength is longer in the visible light region. In the present invention, the retardation ratio at a predetermined wavelength in the normal direction of the retardation film made of a liquid crystal film containing a dichroic dye is the normal direction of the retardation film made of a liquid crystal film containing no dichroic dye. By making the retardation ratio larger than the retardation ratio at a predetermined wavelength, a retardation plate in which the extraordinary ray refractive index ne or birefringence Δn has “negative dispersion” characteristics can be realized.

In the present invention, the retardation at a predetermined wavelength in the normal direction of the retardation plate made of a liquid crystal film containing a dichroic dye is Δna · da, and the liquid crystal film is obtained by removing the dichroic dye from the liquid crystal film. When the retardation in the normal direction of the phase difference plate is Δnb · db, the following mathematical formula (1):
Δna · da (580) / Δna · da (550) −Δnb · db (580) / Δnb · db (550)> 0 (1)
(Here, the retardation is represented by the product of birefringence Δn and the thickness d of the retardation plate, and Δna · da (580) and Δna · da (580) are retardations of each retardation plate at a wavelength of 580 nm). Δna · da (550) and Δna · da (550) are retardations of each phase difference plate at a wavelength of 550 nm.)
It is preferable to satisfy.

The retardation plate is a retardation plate characterized in that the birefringence Δn has a “negative dispersion” characteristic that increases in the visible light region as the measurement wavelength is longer. More specifically, when the retardation of the liquid crystal film at 500 nm, 550 nm, and 600 nm is Δn · d (500), Δn · d (550), and Δn · d (600), the following formulas (2) and (3 ):
0.80 <Δn · d (500) / Δn · d (550) <1.00 (2) and 1.00 <Δn · d (600) / Δn · d (550) <1.15 (3) Preferably there is. Here, the retardation is represented by the product (Δn · d) of birefringence Δn and the thickness d of the retardation plate. More preferably, 0.90 <Δn · d (500) / Δn · d (550) <0.98 (2-1)
And 1.02 <Δn · d (600) / Δn · d (550) <1.10 (3-1)
It is. If it is in the range of these values, for example, when using as a quarter wavelength plate, when a linearly polarized light of 400 to 700 nm is incident on this film, a completely circular polarized light is obtained in the polarization state.

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 plate is preferably 20 nm to 500 nm (more preferably 50 nm to 300 nm). The retardation value (Δn · d) referred to here is an in-plane apparent retardation value with respect to light having a wavelength of 550 nm when viewed from the normal direction of the liquid crystal film. That is, in the liquid crystal film obtained by fixing the nematic hybrid orientation structure, since the refractive index in the direction parallel to the director (n _e) and the direction perpendicular refractive index (n _o) is different, from n _e n _o The subtracted value is the apparent birefringence, and the retardation value is given as the product of the birefringence and the absolute film thickness. Such retardation value is measured using an apparatus capable of measuring birefringence (for example, trade name “Axoscan” manufactured by Axometrix, trade name “KOBRA-21ADH” manufactured by Oji Scientific Instruments), etc.) Values can be adopted.

<Liquid crystal film>
The liquid crystal film includes a polymerizable liquid crystal composition and at least one dichroic dye, and has an alignment structure in which a liquid crystal compound is nematic hybrid aligned. A liquid crystal film is a film obtained by aligning and fixing a liquid crystal compound in a liquid crystal state. The orientation of the liquid crystal film indicates a state in which the molecular chains of the liquid crystal compound are arranged in a specific direction, and this state can be measured by measuring the phase difference (Δn · d) of the liquid crystal film. The orientation refers to, for example, Δn · d of 20 nm or more at a measurement wavelength of 550 nm. Δn · d is the product of birefringence Δn and film thickness d.

  FIG. 14 shows a cross-sectional structure of the liquid crystal film of the present invention having an alignment structure in which a liquid crystal compound is nematic hybrid aligned. In the liquid crystal film having a nematic hybrid alignment structure, the director of the polymerizable liquid crystal compound is oriented at different angles at all positions in the film thickness direction. Accordingly, the retardation plate of the present invention no longer has an optical axis when viewed as a film structure. FIG. 15 shows definitions of the tilt angle and twist angle of the liquid crystal molecules. Here, the tilt direction (axis) of the liquid crystal film refers to a liquid crystal molecule director and a projection component onto the c plane of the director when the c plane is viewed from the b plane through the liquid crystal film as shown in FIG. A direction in which the angle is an acute angle and parallel to the projection component is defined as a tilt direction (axis).

  As the nematic hybrid alignment structure fixed in the liquid crystal film, the angle formed by the director of the liquid crystal molecules and the film plane in the vicinity of one film interface of the liquid crystal film is usually 20 to 90 degrees as an absolute value, preferably 30. In the vicinity of the film interface opposite to the film surface, the angle is usually 0 to 50 degrees as an absolute value, preferably 0 to 30 degrees. The average tilt angle in the alignment structure is usually 5 to 45 degrees as an absolute value, preferably 10 to 40 degrees, and most preferably 15 to 35 degrees. If the average tilt angle is within the above numerical range, the reflective viewing angle characteristics can be improved when the liquid crystal display device or the organic EL display device is provided in combination with a polarizing plate. Here, the average tilt angle means the average value of the angle formed by the director of the liquid crystal molecules and the film plane in the film thickness direction of the liquid crystal film.

The retardation plate of the present invention may be a liquid crystal film in which a twisted nematic hybrid alignment structure is fixed. A liquid crystal film in which twisted nematic hybrid alignment is fixed has a structure in which a director of liquid crystal molecules twists an optically anisotropic axis from one surface to the other surface. Therefore, this retardation plate has characteristics equivalent to those obtained by stacking optically anisotropic layers in multiple layers so that the optical anisotropic axis is continuously twisted, and is a normal TN (twisted nematic). ) Like liquid crystal cells and STN (super twisted nematic) liquid crystal cells, the retardation value (= Δnd: value represented by the product of birefringence Δn and thickness d) and twist when viewed from the normal direction of the film Has horns. Furthermore, the liquid crystal film with a fixed twisted nematic hybrid alignment structure is different in the film thickness direction, while the director of the liquid crystal molecules is twisted in the in-plane direction from one side to the other side of the liquid crystal molecule. It is a film inclined at an angle. The twist angle in the alignment structure is usually 0 to 70 degrees as an absolute value, preferably 0 to 60 degrees, and most preferably 0 to 59 degrees. If the twist angle deviates more than 70 degrees, such as contrast and antireflection performance when the liquid crystal display device or organic EL display device is combined with a polarizing plate, the display characteristics when viewed from the front, etc. There is a fear. Here, although there are two types of twist angles, the twist angle may be either the right twist or the left twist.
Such retardation value, twist angle, and tilt angle can be measured by a device capable of measuring birefringence (for example, trade name “Axoscan” manufactured by Axometrics, trade name “KOBRA-21ADH” manufactured by Oji Scientific Instruments, etc.) ) Can be calculated from the value measured using

<Dichroic dye>
The dichroic dye used in the present invention will be described.
A dichroic dye refers to a dye having the property that the absorbance in the major axis direction of a 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. A plurality of these dyes may be used, a plurality of pigments may be used, or a dye and a pigment may be combined. Furthermore, 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.
The dichroic dye preferably has a maximum absorption wavelength (λmax) in the range of 380 to 780 nm, more preferably 400 to 750 nm, still more preferably 450 to 700 nm, and most preferably 540 to 620 nm. When the retardation film of the present invention is applied to an image display device, it is preferable to select the maximum absorption wavelength in consideration of the emission spectrum of the light source of the image display device.

  FIG. 13 shows the emission spectrum of the organic electroluminescence display device when the red, blue, and green emission spectra and the three colors are turned on simultaneously to display white. As shown in FIG. 13, blue has an emission spectrum having a maximum value at about 460 nm, green at 530 nm, and red at 630 nm. When the retardation plate of the present invention is applied to this organic electroluminescence display device, absorption by the dichroic dye is inevitable, but in order to minimize the decrease in transmittance due to this absorption, It is preferable to select a dichroic dye having a maximum absorption at a wavelength deviating from the maximum wavelength of the emission spectrum. For example, a dichroic dye having a maximum absorption wavelength near 580 nm as shown in FIG. 11 may be applied. it can. 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 outside the maximum value of the emission spectrum of the LED using the maximum absorption wavelength of the dichroic dye. Can do. The difference between the maximum absorption 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, more preferably 20 nm or more. If it is 5 nm or more, the transmittance | permeability fall by removing a wavelength can be suppressed.

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. It 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 or more and 50 or less, more preferably 5 or more and 30 or less.
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 formula (1), n is an integer of 1 to 4. Ar ₁ and Ar ₃ are each independently selected from the groups shown below.

Ar ₂ is selected from the following groups, and when n in the formula (1) is 2 or more, Ar ₂ may be the same as or different from each other.

（ｍは０〜１０の整数であり、同一の基中にｍが２つある場合、この２つのｍは互いに同一でも異なっていてもよい。）A ₁ and A ₂ are each independently selected from the groups shown below.

(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), the formula (1-2), the formula (1-5), the formula (1-6), the formula (1-8), the formula (1-10), the 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 (1-57) and the formula (1-58) are more preferable than those respectively represented by formula (1-2), formula (1-5), (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.

The anthraquinone dye is preferably a compound represented by the formula (1-59).

In formula (1-59), R ^{1 to} R ⁸ each independently represent a hydrogen atom, —Rx, —NH ₂ , —NHRx, —NRx ₂ , —SRx, —OH, or a halogen atom. Rx represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms.

The acridine dye is preferably a compound represented by the formula (1-60).

In formula (1-60), R ^{16 to} R ²³ each independently represent a hydrogen atom, —Rx, —NH ₂ , —NHRx, —NRx ₂ , —SRx, or a halogen atom. Rx represents an alkyl group having 1 to 6 carbon atoms 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 formula (1-61), R ^{9 to} R ¹⁵ each independently represent a hydrogen atom, —Rx, —NH ₂ , —NHRx, —NRx ₂ , —SRx, —OH, or a halogen atom. Rx represents an alkyl group having 1 to 6 carbon atoms 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.

As the cyanine dye, a compound represented by the formula (1-62) and a compound represented by the formula (1-63) are preferable.

In Formula (1-62), D ¹ and D ² each independently represent a group represented by any of the following Formulas (1-62a) to (1-62d), and n5 is from 1 to 3 Represents an integer.

In Formula (1-63), D ³ and D ⁴ each independently represent a group represented by any of Formula (1-63a) to Formula (1-63h), and n6 is an integer of 1 to 3. Represents.

  As mentioned above, although the preferable example was demonstrated about the dichroic dye which the said retardation plate contains, the dichroic dye which this composition for partial retardation plates contains is an azo dye (1). Preferably, at least two kinds of azo dyes (1) having different maximum absorption wavelengths may be contained.

  The content of the dichroic dye in the retardation plate can be adjusted as appropriate according to the type of the dichroic dye, and is, for example, 0.1 part by weight or more and 50 parts by weight with respect to 100 parts by weight of the liquid crystal composition. Parts by weight or less, preferably 0.1 parts by weight or more and 20 parts by weight or less, more preferably 0.1 parts by weight or more and 10 parts by weight or less. When the content of the dichroic dye is within this range, the liquid crystal composition can be formed or polymerized without disturbing the alignment of the liquid crystal compound. If content of a dichroic dye is 50 mass parts or less, the fall of the transmittance | permeability of the film by absorption of a pigment | dye can be suppressed. If the content of the dichroic dye is 0.1 parts by mass or more, the refractive index can be controlled and sufficient optical characteristics can be obtained. Therefore, the content of the dichroic dye can be determined within a range in which the liquid crystal compound can maintain the alignment. In addition, when using 2 or more types of dichroic dyes, content of a dichroic dye is content of the sum total of the used dichroic dye.

<Polymerizable liquid crystal composition>
The polymerizable liquid crystal composition used in the present invention will be described.
Such a polymerizable liquid crystal compound is not particularly limited as long as it is a liquid crystalline 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.

  In the present invention, a known polymerizable liquid crystal compound can be appropriately used. Moreover, as such a polymerizable liquid crystal compound, it is preferable to use a polymerizable liquid crystal compound that can be nematic hybrid aligned on a substrate to fix the alignment state. Furthermore, as such a polymerizable liquid crystal compound, for example, a low molecular weight polymerizable liquid crystal compound (a liquid crystalline monomer having a polymerizable group), a high molecular weight polymerizable liquid crystal compound (a liquid crystalline polymer having a polymerizable group), And mixtures thereof can be used as appropriate.

  Moreover, as such a polymerizable liquid crystal compound, a 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 components (liquid crystal compound, etc.) present around it by light and / or heat to fix the alignment. The kind is not specifically limited, A liquid crystal compound provided with a well-known polymeric group can be utilized suitably. 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), W independently represents any one of H and CH ₃ . Depending on the type of W, a group represented by CH ₂ = CWCOO in the formula is either an acrylate group or a methacrylate group.
Moreover, in formula (10)-(12), n is an integer of 1-20 (more preferably 2-12, still more preferably 3-6). 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 of the compound derived from the liquid crystal necessary for realizing good nematic hybrid alignment is achieved. As a result, good nematic hybrid alignment can be realized.

In the general formula (10), R ^a is 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 the number of carbon atoms is within the above numerical range, the liquid crystal-derived fluidity necessary to achieve good nematic hybrid alignment is maintained, and as a result, good nematic hybrid alignment can be realized. In addition, the temperature range in which the compound exhibits liquid crystallinity tends to be widened. Such an alkyl group may be linear, branched, or cyclic, and is not particularly limited, but it can realize a good nematic hybrid orientation. From a viewpoint, it is more preferable that it is a linear thing.
Moreover, as for the C1-C20 alkoxy group which can be selected as said 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, the liquidity derived from the liquid crystal of the compound necessary for realizing good nematic hybrid alignment is maintained, and as a result, good nematic hybrid alignment can be realized. In addition, the temperature range in which the compound exhibits liquid crystallinity tends to be 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 it may be sufficient and it does not restrict | limit, From a viewpoint of implement | achieving favorable nematic hybrid orientation, it is more preferable that it is a linear thing.

In the general formula (12), Z ¹ and Z ² are each independently any group of —COO— and —OCO—. Such Z ¹ and Z ² are groups in which ^one of Z ¹ and Z ² is represented by —COO—, and the other group is — A group represented by OCO- is preferable. Further, in the general formula (12), ^{X 1} and ^{X 2} are each independently, H, and carbon atoms exhibits any of the alkyl group having 1 to 7. 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, and the alkyl group is 1 (the alkyl group is CH ₃ . Is more preferable. If the number of carbon atoms is within the above numerical range, a good nematic hybrid orientation can be realized. Thus, it is particularly preferable that 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.
Thus, in the case where the compounds represented by the general formulas (10) to (12) are combined and used 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). When the content of the compound represented by the general formula (10) is within the above numerical range, it is possible to suppress the occurrence of alignment defects with respect to nematic hybrid alignment.

  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 nematic hybrid 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 the content of the compound represented by the general formula (12) is within the above numerical range, it is possible to suppress the occurrence of alignment defects with respect to nematic hybrid alignment.

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

  Further, the method for producing such a polymerizable liquid crystal compound is not particularly limited, and a known method can be appropriately used. For example, in the case of producing a compound represented by the general formula (110), For example, the method described in British Patent Application Publication No. 2,280,445 may be adopted. In the case of producing the compound represented by the above general formula (111), for example, D.I. J. et al. The method described on pages 3201 to 3215 of “Makromol. 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 No. 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 singly or in combination of two or more.

In the present invention, the phase difference Δn · d is expressed by the following mathematical formulas (2) and (3):
0.80 <Δn · d (500) / Δn · d (550) <1.00 (1)
1.00 <Δn · d (600) / Δn · d (550) <1.15 (2)
It is preferable to satisfy. In particular, as a method of satisfying 0.80 <Δn · d (500) / Δn · d (550) <1.00, the polymerizable liquid crystal compound is a compound having two or more kinds of mesogenic groups, and at least one of them. By aligning the mesogenic group in a direction substantially orthogonal to the slow axis of the homogeneous alignment of the liquid crystal layer, the longer the wavelength, the larger the phase difference, as disclosed in JP-A-2002-267838 and JP-A-2010-31223. It is described in the gazette. In the present invention, at least one mesogen group of a liquid crystal compound having two or more kinds of mesogenic groups is aligned in a direction substantially orthogonal to the optical axis direction of the rod-shaped liquid crystal compound, whereby the liquid crystal film contains a polymerizable dichroic dye. Even when not added, it has negative dispersion characteristics.
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 compound (molecular structure relating to liquid crystallinity of the rod-like liquid crystal compound). The mesogenic group in the rod-like liquid crystal compound 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. WO2012 / 169424 and the like.

Specific examples of the compound having two or more kinds of mesogenic groups include the following compounds.

In order to induce twisted nematic alignment of the liquid crystal compound, a chiral agent is added to the liquid crystal composition, or a liquid crystal compound or a non-liquid crystal compound having at least one chiral structural unit is added to the liquid crystal composition. It is particularly desirable to blend.
Examples of the chiral structural unit include optically active 2-methyl-1,4-butanediol, 2,4-pentanediol, 1,2-propanediol, 2-chloro-1,4-butanediol, and 2-fluoro. -1,4-butanediol, 2-bromo-1,4-butanediol, 2-ethyl-1,4-butanediol, 2-propyl-1,4-butanediol, 3-methylhexanediol, 3-methyl Units derived from adipic acid, naproxen derivatives, camphoric acid, binaphthol, menthol or cholesteryl group-containing structural units or derivatives thereof (for example, derivatives such as diacetoxy compounds) can be used. The diols may be either R-form or S-form, and may be a mixture of R-form and S-form. These structural units are merely examples, and the present invention is not limited thereto. In addition, even in the case of oligomers and low-molecular liquid crystals, thermal crosslinking, photocrosslinking, etc. in a state where the alignment is fixed by cooling to below the liquid crystal transition temperature or liquid crystal transition temperature by introducing a crosslinkable group or blending of appropriate crosslinking agents. Those that can be polymerized by the above means are also included in the liquid crystal polymer.

  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.

  As described above, the polymerizable liquid crystal composition may use a mixture of a liquid crystal compound having a polymerizable group and another polymerizable compound that does not exhibit liquid crystallinity. Such other polymerizable compounds 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. Not. For example, a known polymerizable compound (polymerizable monomer) can be used as appropriate, and a suitable monomer may be selected from 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 amount of the other polymerizable monomer added is 0.5 to 50 parts by weight based on 100 parts by weight of the total amount of the liquid crystal compound having the polymerizable group and the other polymerizable monomer not exhibiting liquid crystallinity. It is preferable to be 1 to 30 parts by weight. Further, 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. Even a discotic liquid crystal compound can be used without any problem. As the liquid crystal polymer, those showing optically positive or negative uniaxiality are usually used. These optical characteristics are appropriately selected depending on the function required for the optical anisotropic element, but in the case of a liquid crystal polymer layer with twisted nematic hybrid alignment, a liquid crystal polymer exhibiting positive uniaxiality is preferably used.

  The polymerization initiator for polymerizing the polymerizable liquid crystal composition and the dichroic dye as described above is not particularly limited, and a known polymerization initiator can be appropriately used. As described above, the polymerization initiator can start the polymerization of the polymerizable liquid crystal compound more efficiently according to the type of the polymerizable liquid crystal compound in the composition from among known polymerization initiators. What is necessary is just to select suitably and use.

  Moreover, even if such a polymerization initiator is a thermal polymerization initiator (an initiator when utilizing a thermal polymerization reaction), a photopolymerization initiator (an initiator when utilizing light or electron beam irradiation) It may be. 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. And 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-aminophenyl ketone 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. .

  In addition, as such a photopolymerization initiator, a commercially available product may be used. For example, a photopolymerization initiator manufactured by Ciba-Geigy (trade name “Irgacure 907”, trade name “Irgacure 651”, trade name) “Irgacure 184”) or 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, etc., a photopolymerization initiator that generates free radicals (for example, trade name “Irgacure 651” manufactured by Ciba-Geigy) or a photopolymerization initiator that generates ions (for example, Union Carbide) A suitable photopolymerization initiator (trade name “UVI6974”) may be appropriately selected and used.

  Further, the content of the polymerization initiator in the mixture of the polymerizable liquid crystal compound and the dichroic dye according to the present invention is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the mixture, and 3 to 5 More preferred are parts by weight. If the content of such a polymerization initiator is within the above numerical range, the resulting retardation plate has sufficient curability and can suppress the occurrence of defects in the alignment of the liquid crystal.

<Method for producing retardation plate>
Next, the manufacturing method of the phase difference plate which consists of a liquid crystal film of this invention is demonstrated.
The method of producing the retardation plate is not limited to these, but the composition containing the polymerizable liquid crystal compound, the dichroic dye and various compounds added as necessary is in a molten state, or A solution of the composition 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 ( By fixing the nematic hybrid alignment using means for fixing the above-described alignment such as polymerization and crosslinking, a liquid crystal film in which the alignment of the liquid crystal and the dichroic dye is fixed is formed.

  In this specification, the alignment state “fixed in a state of nematic hybrid alignment” means that the liquid crystal film obtained by polymerizing the polymerizable liquid crystal compound to fix the alignment is nematic hybrid alignment (of liquid crystal molecules). The director refers to confirming that the director is seen from the film thickness direction (preferably at every location) and is oriented at different angles, and the component derived from the polymerizable liquid crystal compound or the like (preferably Is a component derived from a polymerizable liquid crystal compound: the polymerizable liquid crystal compound itself, a composition formed by decomposing the polymerizable liquid crystal compound, a polymer of the polymerizable liquid crystal compound, or the like). However, what is necessary is just to be fixed in the state of nematic hybrid orientation. In the present specification, the “nematic hybrid structure” refers to an alignment structure in which a liquid crystal compound is nematic hybrid aligned in a liquid crystal film.

  The solvent used for the preparation of the solution is not particularly limited as long as it is a solvent that can dissolve the polymerizable liquid crystal composition of the present invention and the dichroic dye and can be distilled off under appropriate conditions. Generally, acetone, methyl ethyl ketone, isophorone, Ketones such as cyclohexanone and cyclopentanone, 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, acetic acid 2 -Glycol ethers such as methoxyethyl, propylene glycol 1-monomethyl ether 2-acetate, esters such as ethyl acetate and ethyl lactate, phenols such as phenol and chlorophenol , N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone and other amides, chloroform, dichloromethane, trichloroethylene, tetrachloroethane, tetrachloroethane, tetrachloroethylene, chlorobenzene, dichlorobenzene, etc. , Heterocycles such as tetrahydrofuran, γ-butyrolactone, aromatic hydrocarbons such as benzene, toluene, zylene, methoxybenzene, 1,2-dimethoxybenzene, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve Etc. or a mixed system thereof is preferably used.

  In addition, as such a solvent, a drying speed suitable for applying the solution so as to obtain a uniform film thickness, ease of handling (harmful to the environment), and dissolution in the polymerizable liquid crystal compound and the dichroic dye. From the viewpoint of properties, propylene glycol 1-monomethyl ether 2-acetate, 2-methoxyethyl acetate, toluene, xylen, methoxybenzene, 1,2-methoxybenzene, cyclohexanone, cyclopentanone, methyl cellosolve, ethyl cellosolve, butyl cellosolve, γ -Butyrolactone is preferable, and propylene glycol 1-monomethyl ether 2-acetate and γ-butyrolactone are more preferable. 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, the content of the solvent used in the present invention is determined by the method of using the composition (for example, when using it to form a liquid crystal film, the method of use including the design of the thickness, the coating method, etc.) It can be adjusted as appropriate. For example, the content of the solvent is preferably 30 to 98% by weight, more preferably 50 to 95% by weight, and still more preferably 70 to 90% by weight. If the content of such a solvent is 30% by mass or more, the amount of the solvent with respect to the mixture of the polymerizable liquid crystal compound and the dichroic dye is ensured, so that the precipitation of the liquid crystal during storage can be suppressed, It is possible to prevent the wettability from being lowered due to an increase in the viscosity of the mixture and to satisfactorily perform coating during the production of the retardation plate. Moreover, if the content of the solvent is 95% by mass or less, the removal time (drying time) does not take long when the solvent is removed, and the production efficiency is reduced when the film is manufactured, Since the fluidity of the surface is suppressed when the mixture is coated on a substrate, a uniform retardation plate can be produced. Thus, in the mixture of the polymerizable liquid crystal compound and the dichroic dye of the present invention, the amount of the mixture of components other than the solvent is preferably 5 to 70% by weight, and 10 to 50% by weight. It is more preferable that it is 10 to 30% by weight.
In order to form a uniform coating film on the alignment substrate, a reaction activator, a sensitizer, a surfactant, an antifoaming agent, a leveling agent, and the like may be added to the solution.

Next, the alignment substrate 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, cyclic to thru Examples thereof include cyclopolyolefin having a norbornene structure, diacetyl cellulose, triacetyl cellulose, cellulose acetate, cellulose propionate, cellulose butyrate, epoxy resin, and phenol resin.

  Some of these films exhibit sufficient alignment ability for the liquid crystal substance used in the present invention without performing treatment for expressing the alignment ability again depending on the production method, but the alignment ability is insufficient, or alignment If the film does not show the performance, etc., these films are stretched under appropriate heating if necessary, the film surface is rubbed in one direction with a rayon cloth, etc., so-called rubbing treatment, polyimide, polyvinyl alcohol, silane on the film An alignment film made of a known alignment agent such as a coupling agent is provided and subjected to rubbing treatment. A photo-alignment film is applied on the film, heated at an appropriate temperature, and then irradiated with linearly polarized ultraviolet rays to form the alignment film. You may use the film which expressed the orientation ability by oblique vapor deposition processing, such as a silicon oxide, or combining these suitably. In addition, a metal plate such as aluminum, iron, or copper having various fine grooves on the surface, various glass plates, or the like can be used as the alignment substrate. Among these, in the field of liquid crystals, it is common to perform a rubbing process that rubs 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 50 or less, the liquid crystal composition can be sufficiently oriented, and the optical characteristics can be sufficiently exhibited.

Next, the coating method 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 differs depending on the content of the solvent in the polymerizable liquid crystal compound of the present invention and the dichroic dye mixture, etc., and cannot generally be said, but the thickness of the coating film before drying. The (wet film thickness) is preferably 3 to 50 μm, and more preferably 5 to 20 μm. If such a thickness (wet film thickness) is 3 μm or more, in order to obtain desired optical characteristics, precipitation of a solid content (liquid crystal compound or the like) in the polymerizable liquid crystal composition is suppressed, and a uniform liquid crystal film is obtained. Moreover, sufficient smoothness of the liquid crystal film can be obtained by uniform coating. Moreover, since the density | concentration of the solid content in a liquid-crystal composition for setting it as a desired optical characteristic will become thin if it is 20 micrometers or less, it can suppress that the drying time after application | coating becomes long.

  In the method of applying a liquid crystal material solution, it is preferable to include a drying step for removing the solvent after the application. This drying step varies depending on the polymerizable liquid crystal compound, dichroic dye, type of solvent, and the like used in the present invention, and is not generally limited, and is 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.). As described above, depending on the type of the solvent, it is possible to produce a liquid crystal film in which the liquid crystal compound is homogeneously oriented 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. If such temperature conditions are 15 ° C. or higher, cooling equipment is not required and efficient production is possible. Moreover, if it is 110 degrees C or less, it can suppress that a base material is distorted with a heat | fever and an optical characteristic etc. change.

Moreover, it does not restrict | limit especially as pressure conditions in this drying process, However, It is preferable that it is 600-1400 hPa, and it is more preferable that it is 900-1100 hPa. If such a pressure condition is 600 hPa or more, drying of the solvent is slow and it is possible to suppress the occurrence of drying unevenness. If the pressure condition is 1400 hPa or less, the time required for drying the solvent can be reduced. 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 second-60 minutes, and it is more preferable to set it as 1 minute-30 minutes. If such a drying time is 10 seconds or more, since the solvent is slowly dried, the smoothness of the liquid crystal film can be maintained. Moreover, if it is 60 minutes or less, a manufacturing speed is quick and sufficient productivity can be maintained. 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 thickness of the applied film in the dry state is 0.1 μm to 50 μm, preferably 0.2 μm to 20 μm. If the film thickness is within the above numerical range, the optical performance of the obtained liquid crystal film can be sufficiently exhibited, and the polymerizable liquid crystal compound and the dichroic dye can be sufficiently aligned.

Next, a method for fixing the orientation will be described.
As a method for polymerizing the polymerizable liquid crystal compound to fix the alignment state, a known method capable of polymerization may be appropriately employed depending on the type of the polymerization initiator used or the type of the polymerizable liquid crystal compound. it can. As a method for fixing such an alignment state (polymerization / fixation), for example, the polymerizable group (reactive property) can be obtained by performing light irradiation and / or heat treatment depending on the kind of the polymerization initiator. A method may be employed in which the orientation is fixed in a homogeneous orientation state by reacting a functional group).

When the polymerization initiator is such that it exhibits the function of the initiator by light irradiation (for example, in the case of a so-called photocation generator), the alignment state of the homogeneous alignment may be fixed by light irradiation. 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. (Medium pressure or high pressure mercury ultraviolet lamp), ultra high pressure mercury lamp, low pressure mercury lamp, xenon lamp, arc lamp, laser, etc.) and irradiating light from the light source. In addition, it becomes possible to activate a reaction 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 these cases, an appropriate photosensitizer and two or more polymerization initiators having different absorption wavelengths are mixed from the viewpoint of fixing (curing) the coating film while maintaining the orientation state more efficiently. For example, a method such as use may be employed. Further, the temperature condition at the time of such light irradiation is not particularly limited as long as the polymerizable liquid crystal compound can maintain a nematic hybrid alignment state. 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 conditions of the atmosphere at the time of such light irradiation are not particularly limited, and may be an air atmosphere or 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.

In addition, when the polymerization initiator is such that the function of the initiator is manifested by heat (for example, in the case of a so-called thermal cation generator), the alignment is fixed in a nematic hybrid alignment state by heat treatment. It is preferable to do. 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.
If the base material has low heat resistance, the polymerization initiator that exhibits the function of an initiator by light irradiation is used, and the alignment state of the nematic hybrid alignment is fixed by light irradiation. It is preferable to do.

  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.

  Thus, after applying the mixture containing the polymerizable liquid crystal compound and the dichroic dye on the alignment substrate, the solvent is removed from the coating film to align the polymerizable liquid crystal compound and the dichroic dye. By fixing the liquid crystal state, a liquid crystal film in which the alignment state is fixed in a nematic hybrid 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, an adhesive is used. 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 it can also be set as the laminated polarizing plate of this invention 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 polarizing film / retardation plate (liquid crystal film) / transparent plastic film.

  Further, as a method for confirming nematic hybrid alignment in the liquid crystal film, the following method may be employed. As a method for confirming such a nematic hybrid alignment, a known method can be appropriately employed, and is not particularly limited. However, a pair of orthogonal polarizing plates (a direction in which one deflecting plate is deflected and a direction in which the other deflecting plate is 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 polarizing plates whose deflection directions are perpendicular to each other, the transmitted light is confirmed with the naked eye. Or a method of observing the retardation plate with a polarizing microscope may be employed. In any case, when the liquid crystal film is a nematic hybrid alignment liquid crystal film, when the incident angle of light incident on the surface of the liquid crystal film in the sample is tilted, the tilt direction When light is incident from a certain tilt angle, the light appears to be brightest due to the phase difference of the light. On the other hand, when the incident angle of light incident on the sample is tilted, the amount of transmitted light is asymmetric in the vertical direction. The brightness appears to change depending on the direction. Therefore, the presence or absence of nematic hybrid alignment 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 nematic hybrid alignment liquid crystal film has different retardation characteristics depending on the incident angle of light as described above, as a method for confirming the nematic hybrid alignment, for example, with respect to the surface of the liquid crystal film, A birefringence measuring apparatus (for example, Axo-metrix) capable of measuring a phase difference in a vertical direction (perpendicular incident angle) and a phase difference when the incident angle of light is tilted from the normal incident angle to a specific angle. Using a product name “Axoscan” manufactured by the company, a product name “KOBRA-21ADH” manufactured by Oji Scientific Instruments, etc.), the viewing angle is increased from 0 degrees (perpendicular to the liquid crystal film). The phase difference is measured while appropriately changing the angle to obtain the phase difference of the sample at a plurality of viewing angles, and in a direction perpendicular to the surface of the liquid crystal film. The phase difference is confirmed, and in the direction in which the viewing angle becomes larger with respect to the surface of the liquid crystal film, the phase difference is confirmed to be asymmetric between the values of the − direction and the + direction of the viewing angle. Based on this, a method of confirming the presence or absence of nematic hybrid alignment may be adopted.

  In addition, the thickness of the liquid crystal film (the thickness of the cured film) varies depending on the application and required characteristics, but is preferably 0.1 to 10 μm, and preferably 0.2 to 5 μm. Is more preferable. If the thickness of such a liquid crystal film is 0.1 μm or more, a desired retardation can be expressed, and if it is 10 μm or less, a decrease in the orientation of the liquid crystal or a decrease in the transmittance due to the dye is suppressed. be able to.

  The birefringence Δn of such a liquid crystal film varies depending on the application and required characteristics, but is preferably 0.005 to 0.5, and more preferably 0.01 to 0.3. If birefringence (DELTA) n is said range, when a film is made into a desired phase difference, thickness can be 10 micrometers or less, Therefore It can use suitably as a phase difference plate and a laminated polarizing plate.

<Laminated polarizing plate>
The laminated polarizing plate used in the present invention is a combination of a retardation plate and a polarizer. As the linear polarizer, 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 preferably has excellent 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 copolymer, and the like. Examples thereof include styrene polymers such as coalesced (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 ZEON Corporation), acrylic film, TPX film (product of Mitsui Chemicals), and acrylprene film (product of Mitsubishi Rayon Co., Ltd.). Triacetyl cellulose, a cycloolefin polymer, and an acrylic polymer are preferable from the viewpoint of planarity, heat resistance, moisture resistance, and the like when a laminated polarizing plate having a function is used.

  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 through an aqueous adhesive or the like. 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 of this invention may serve as the protective film of a polarizer.

As the protective film, a hard coat layer, an antireflection treatment, an anti-sticking treatment, or a treatment subjected to diffusion or anti-glare treatment can be used.
The hard coat treatment is applied for the purpose of preventing scratches on the surface of the laminated polarizing plate. For example, a hard film with an excellent UV curable resin such as acrylic or silicone is used to protect the cured film with excellent hardness and sliding properties. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the laminated polarizing plate, and can be achieved by forming an antireflection film or the like according to the related art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the laminated polarizing plate and obstructing the visibility of the light transmitted through the laminated polarizing plate. 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 surface method or a compounding method of transparent fine particles. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include conductive materials composed of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter 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 laminated polarizing plate can be prepared by laminating a retardation plate and a polarizer to each other via an adhesive layer. If the retardation plate comprises the liquid crystal film, a polymerizable liquid crystal compound and It can be produced by applying a mixture of dichroic dyes directly or through an alignment film on a polarizer of a polarizing plate 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.

  When two or more liquid crystal films are bonded to each other through the pressure-sensitive adhesive layer, the film surface can be surface-treated to improve the adhesion with the pressure-sensitive adhesive layer. 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 liquid crystal film can be suitably employed. Among these surface treatment methods, corona discharge treatment is good.

  Since the retardation plate of the present invention is a liquid crystal film in which a nematic hybrid alignment structure is fixed, the upper and lower sides of the liquid crystal film are not optically equivalent. Therefore, as a laminated polarizing plate having the function of elliptically polarized light or circularly polarized light, the display performance varies depending on which film surface of the liquid crystal film is placed on the polarizing plate side and in combination with optical parameters such as a liquid crystal cell. Although the present invention does not limit which film side of the liquid crystal film is on the polarizing plate side, the optical characteristics required for the laminated polarizing plate having the function of elliptically polarized light or circularly polarized light, and the function of the elliptically polarized light or circularly polarized light are also provided. In view of the display characteristics required for the liquid crystal display device and the organic EL display device having the laminated polarizing plate, the configuration of the laminated polarizing plate having the elliptically polarizing function of the present invention, the liquid crystal display device, and the organic EL display device It is desirable to determine the arrangement conditions and the like.

<Display device>
The display device of the present invention includes the retardation plate of the present invention and a laminated polarizing plate having a function of elliptically polarized light or circularly polarized light composed of the retardation plate and a polarizer. Such a display device of the present invention only needs to include the retardation plate of the present invention, and the type of the display device is not particularly limited, and is an image display device, a liquid crystal display device, an organic EL display device, a plasma display. A known display device such as can be used as appropriate. Further, the method of arranging the retardation plate of the present invention on the display device is not particularly limited, and a known method can be appropriately used.

A liquid crystal display device to which the retardation plate of the present invention is applied will be described.
The liquid crystal display device of the present invention has at least the retardation plate. A liquid crystal display device is generally composed of a polarizer, 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 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 having the property of aligning the liquid crystal itself, a substrate itself lacking alignment ability, but a transparent substrate provided with an alignment film having the property of aligning liquid crystal, etc. Can also 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, polymer 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 for forming various types of liquid crystal cells described later.

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

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 of the present invention including the phase plate of the present invention has a desired birefringence wavelength dispersion characteristic because the phase difference plate has a desired birefringence wavelength dispersion characteristic. Thus, it is possible to sufficiently improve the luminance and the like, and thereby the viewing angle and the image quality can be sufficiently improved.

An organic electroluminescence device (organic EL display device) including the retardation plate of the present invention 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 fluorescent 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 linear polarizer 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 surface of the metal electrode is completely shielded by forming a circularly polarizing plate (laminated polarizing plate) in which the retardation plate is a quarter-wave plate and a linear polarizer and a retardation plate are combined. Can do.
That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the linear polarizer. This linearly polarized light is generally elliptically polarized by the phase difference plate. In particular, when the phase difference plate is a quarter wavelength plate and the angle between the polarization directions of the linear polarizer and the phase difference plate is π / 4, Become.

  This circularly polarized light passes through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, passes through the organic thin film, the transparent electrode, and the transparent substrate again, and becomes linearly polarized light again on the retardation plate. Since this linearly polarized light is orthogonal to the polarization direction of the linear polarizer, it cannot be transmitted through the polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded. When the angle formed by the absorption axis of the polarizing plate and the slow axis of the quarter-wave plate is p, the circular polarizing plate is formed by combining a linear polarizing plate with a quarter-wave plate. When the retardation plate of the invention is nematic hybrid orientation, it is usually in the range of 40 to 50 degrees, preferably 42 to 48 degrees, and more preferably about 45 degrees. If it is in the said numerical range, sufficient antireflection effect will be acquired and the fall of an image quality can be suppressed. When the retardation plate of the present invention is twisted nematic hybrid alignment, it is necessary to change the angle formed by the absorption axis of the polarizing plate and the slow axis of the quarter-wave plate depending on the twist angle. It is difficult to specify the range.

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) Microscope observation 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%. Wavelength region 440-1
A spectrum at 00 nm was measured.
(3) Birefringence measurement It measured using the automatic birefringence meter Axoscan by Axometrics.
(4) Polarization absorption spectrum of dichroic dye Measurement was performed using a spectrum (V-570) manufactured by JASCO Corporation.
(5) Reflection viewing angle measurement The viewing angle characteristics of the reflectance when viewed from the front and oblique directions of the organic EL display device were measured using a reflection viewing angle measurement device EZ-CONTRAST manufactured by ELDIM.

Example 1
<Preparation of mixed solution of polymerizable liquid crystal compound (A) and dichroic dye>
A rod-shaped liquid crystal compound (21) represented by the following formula and a compound (22) having two or more kinds of mesogenic groups were prepared. 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.

Next, 17.6 parts by weight of the rod-shaped liquid crystal compound (21) and 2 parts by weight of the compound (22) having two or more kinds of mesogenic groups are mixed to obtain a first mixture (polymerizable liquid crystal compound (A)). ) Next, with respect to the first mixture, a dichroic dye (Nagase Sangyo Co., Ltd., G-241, trisazo dye, maximum absorption wavelength 560 nm) in a ratio of 0.08 parts by weight with respect to 100 parts by weight in total. Furthermore, a polymerization initiator (Ciba-Geigy, Irgacure 651, solid at room temperature (25 ° C.)) is added to 100 parts by weight of the total amount of the polymerizable liquid crystal compound (A) and the dichroic dye. Was added at a ratio of 3 parts by weight to obtain a second mixture (solid) obtained by mixing the polymerizable liquid crystal compound (A), the dichroic dye and the polymerization initiator.
Next, the second mixture is dissolved in chlorobenzene (solvent), the insoluble matter is filtered through a polytetrafluoroethylene (PTFE) filter having a pore size of 0.45 μm, and the polymerizable liquid crystal compound (A), A mixed solution (third mixture) containing a dichroic dye, a polymerization initiator, and a solvent was obtained. In producing the third mixture, the content of the solvent in the third mixture is 67% by weight, and the polymerizable liquid crystal compound (B), the dichroic dye, the polymerization initiator, The solvent was used so that the total amount of was 33% by weight.

<Production of liquid crystal film>
The alignment substrate was prepared as follows. A polyethylene naphthalate film (manufactured by Teijin Limited, PEN) having a thickness of 38 μm 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.

On the alignment substrate thus obtained, the rod-shaped liquid crystal compound (21) obtained as described above, the compound (22) having two or more kinds of mesogenic groups, a dichroic dye and a polymerization initiator, A mixed solution (third mixture) containing a solvent was applied (coated) by a spin coating method to form a coating film (wet film thickness: 5 μm) to obtain a laminate of the coating film and the alignment substrate.
Next, the laminate of the coating film and the alignment substrate was gradually cooled from pressure: 1013 hPa, temperature: 72 ° C. to 62 ° C. over 10 minutes, and the solvent was removed from the coating film by drying (solvent removal step), followed by room temperature. Quenched until.
Next, with respect to the coating film dried by the solvent removal step, using a high-pressure mercury lamp with an illuminance of 15 mW / cm ² , the integrated irradiation amount is 200 mJ / cm ^2, and ultraviolet light (however, Laminate in which the liquid crystal compound is polymerized (cured) to fix the alignment state, and the alignment state is fixed on the alignment substrate. A body (laminated body of liquid crystal film and alignment substrate) was obtained.

Since the PET film used as the substrate has a large birefringence and is not preferable as an optical film, the liquid crystal film on the obtained alignment substrate is converted to a triacetyl cellulose (TAC) film (Fuji Film) via an ultraviolet curable adhesive. And Z-TAC, 40 um). That is, after the adhesive is applied on the cured liquid crystal film layer on the PET film so as to have a thickness of 5 μm, laminated with the TAC film, and the adhesive is cured by irradiating ultraviolet rays from the TAC film side. The alignment substrate was peeled off.
When the obtained optical film (liquid crystal film / adhesive layer / TAC) was observed under a polarizing microscope, it was found that there was no disclination (orientation defect) and the monodomain was uniformly oriented.

The wavelength dispersion characteristic of retardation (Δnd) in the in-plane direction of the laminate of the TAC film and the liquid crystal film and the TAC film alone was measured using a trade name “Axoscan” manufactured by Axometrix, and the liquid crystal film layer was subtracted from both. The wavelength dispersion characteristics of the birefringence of was measured. FIG. 16 summarizes the birefringence wavelength dispersion characteristics of the liquid crystal film layer, and Table 2 summarizes the optical characteristics results. Δn · d at 550 nm is 138 nm, Δn · d (500) / Δn · d (550) = 0.96, Δn · d (580) / Δn · d (550) = 1.02, and Δn D (600) / Δn · d (550) = 1.03.
Further, the retardation (Δnd) when the obtained optical film was tilted in the rubbing direction (the alignment direction of liquid crystal molecules) was measured using “Axoscan”. The measurement results are shown in FIG. As shown in FIG. 17, it has a viewing angle dependency that is asymmetrical to the left and right, and is found to be tilted. The obtained optical film was confirmed to be a nematic hybrid alignment film, not a uniform tilt alignment, by the method described in Examples of JP-A No. 11-194325. The average tilt angle was 34 degrees.

<Antireflection performance evaluation of organic EL display>
The obtained optical film is made of acrylic resin so that the commercially available polarizing plate 1 (manufactured by Sumitomo Chemical Co., Ltd., SRW062), the absorption axis 2 of the polarizing plate 1 and the tilt direction 5 of the liquid crystal layer 4 in the optical film 3 are 45 degrees. The circularly polarizing plate 7 was produced by pasting together via an adhesive. At the time of bonding, the TAC film 6 side was laminated so as to be in contact with the polarizing plate 1. FIG. 18 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 1 and the liquid crystal layer 4 of the optical film 3. In the liquid crystal layer in the optical film 3, the surface on which the liquid crystal molecules rise more is on the side of the polarizing plate 1, and the surface on which the liquid crystal molecules lie further is on the side opposite to the polarizing plate 1.

The obtained circularly polarizing plate 7 was stuck on a transparent glass substrate of an organic EL element of a commercially available organic EL display via an acrylic pressure-sensitive adhesive to produce the organic EL display device of the present invention. As a result, it was found that an organic EL display device that exhibits a significant effect of preventing external light reflection and has excellent visibility as compared with the case where the circularly polarizing plate 7 is not disposed can be obtained.
In addition, FIG. 19 and Table 2 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident using a reflection viewing angle measuring device EZ-CONTRAST manufactured by ELDIM and the front reflectance.
Moreover, the emission spectrum of this organic EL display device is a graph shown in FIG. 13, and even when the produced optical film is bonded, the transmittance is reduced to about 3% as compared with the case of bonding in Comparative Example 2. It was confirmed that

(Example 2)
<Antireflection performance evaluation of organic EL display>
For the optical film produced in Example 1, the tilt direction 5 of the commercially available polarizing plate 1 (manufactured by Sumitomo Chemical Co., SRW062), the absorption axis 2 of the polarizing plate 1 and the liquid crystal layer 4 in the optical film 3 is 45 degrees. In this manner, the circularly polarizing plate 8 was produced by pasting together through an acrylic adhesive. At the time of bonding, the layers were laminated so that the liquid crystal layer 4 side was in contact with the polarizing plate 1. FIG. 20 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 1 and the liquid crystal layer 4 of the optical film 3. The nematic hybrid structure is the reverse of the case of Example 1, and the liquid crystal layer 4 in the optical film 3 has a surface on which the liquid crystal molecules lie more on the polarizing plate 1 side, and a surface on which the liquid crystal molecules stand more. On the opposite side to the polarizing plate 1.
The obtained circularly polarizing plate 8 was attached to a transparent glass substrate of an organic EL element of a commercially available organic EL display in the same manner as in Example 1 via an acrylic pressure-sensitive adhesive, and the organic EL display device of the present invention was attached. Created. 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.
21 and Table 2 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident by EZ-CONTRAST and the front reflectance.

(Example 3)
<Production of liquid crystal film>
The third mixture prepared in Example 1 was applied by spin coating on an alignment substrate prepared in the same manner as in Example 1, to form a coating film (wet film thickness: 2.5 um). And a laminated body of the alignment substrate was obtained. Since the substrate used on the laminate has a large birefringence with polyethylene naphthalate, the liquid crystal film layer was peeled and transferred to the TAC film in the same manner as in Example 1, and the laminate composed of TAC / adhesive / liquid crystal film. Got the body. When the wavelength dispersion characteristic of retardation (Δn · d) in the in-plane direction of the laminate and the average tilt angle by measuring the phase difference in the oblique direction were measured, Δn · d at a wavelength of 500 nm was 69 nm, and the average tilt angle was It was 34 degrees, and the wavelength dispersion characteristic of birefringence coincided with the graph (FIG. 16) of the optical film produced in Example 1.
Further, a second PVA layer was formed on the liquid crystal coating film of the laminate by the same method as in Example 1, and an alignment treatment was performed by rubbing in a direction antiparallel to the first PVA layer. The film thickness of the obtained PVA layer was 1.2 μm. On the PVA layer thus obtained, the third mixture prepared in Example 1 was applied by the same method by spin coating, solvent removal by drying, and ultraviolet light irradiation were performed to obtain a liquid crystal film / PVA alignment film. A laminate comprising: / liquid crystal film / PVA alignment film / PEN substrate was obtained. Furthermore, it transferred to the TAC film by the same method as in Example 1 to obtain a laminate composed of TAC / adhesive / liquid crystal film / PVA alignment film / liquid crystal film. The wavelength dispersion characteristic of retardation (Δnd) in the in-plane direction of the obtained liquid crystal film laminate and the TAC film alone was measured using Axoscan, and the birefringence wavelength dispersion characteristic of the liquid crystal film layer was subtracted from both. It was measured. Δn · d at a wavelength of 550 nm was 138 nm, and the chromatic dispersion characteristics coincided with the graph of the optical film produced in Example 1 (FIG. 16).
FIG. 22 shows the measurement results of retardation (Δnd) when the obtained optical film is tilted in the rubbing direction (the alignment direction of liquid crystal molecules). As shown in FIG. 22, since it is bilaterally symmetric and has almost no viewing angle dependency, it is presumed that two liquid crystal layers are laminated in a tilted orientation antiparallel as shown in FIG.

<Antireflection performance evaluation of organic EL display>
For the optical film produced in Example 3, the tilt direction 5 of the commercially available polarizing plate 1 (manufactured by Sumitomo Chemical Co., SRW062), the absorption axis 2 of the polarizing plate 1 and the liquid crystal layer 4 in the optical film 9 is 45 degrees. Thus, the circularly polarizing plate 10 was produced by pasting together through an acrylic adhesive. At the time of bonding, the optical film 9 was laminated so that the liquid crystal layer 4 side was in contact with the polarizing plate 1. FIG. 23 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 1 and the liquid crystal layer 4 of the optical film 9. The nematic hybrid structure is the reverse of the case of Example 1, and the liquid crystal layer 4 in the optical film 9 has a surface on which the liquid crystal molecules lie more on the polarizing plate 1 side and a surface on which the liquid crystal molecules stand more. On the opposite side to the polarizing plate 1.
The obtained circularly polarizing plate 10 was attached to a transparent glass substrate of an organic EL element of a commercially available organic EL display in the same manner as in Example 1 via an acrylic pressure-sensitive adhesive, and the organic EL display device of the present invention was attached. Created. 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.
In addition, FIG. 24 and Table 2 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident with EZ-CONTRAST and the front reflectance.

(Example 4)
<Preparation of mixed solution of polymerizable liquid crystal compound (B) and dichroic dye>
A first mixture (polymerizable liquid crystal compound (1)) obtained by mixing 17.6 parts by weight of the rod-shaped liquid crystal compound (21) prepared in Example 1 and 2 parts by weight of the compound (22) having two or more kinds of mesogenic groups. A)), except that a fourth mixture (polymerizable liquid crystal compound (B)) in which 0.15% by weight of a polymerizable liquid crystal compound (manufactured by BASF, Palicolor LC756) was used as a twist dopant was used. A mixed solution was prepared by various methods.

<Production of liquid crystal film>
The prepared fourth mixture (polymerizable liquid crystal compound (B)) was transferred to a TAC film in the same manner as in Example 1 to obtain an optical film (liquid crystal film / adhesive layer / TAC). The wavelength dispersion characteristic of retardation (Δnd) in the in-plane direction of the obtained liquid crystal film laminate and the TAC film alone was measured using Axoscan, and the birefringence wavelength dispersion characteristic of the liquid crystal film layer was subtracted from both. It was measured. Δn · d at a wavelength of 550 nm was 209 m, and the twist angle was 55 degrees. The retardation (Δnd) when the obtained optical film was tilted in all directions was measured, and it was confirmed that the optical film had an asymmetric viewing angle dependency. It is presumed that the liquid crystal layer is nematic hybrid aligned while being twisted in the film thickness direction. The tilt angle was 25 degrees.

<Antireflection performance evaluation of organic EL display>
The optical film produced in Example 4 is obtained by using a commercially available polarizing plate 1 (manufactured by Sumitomo Chemical Co., SRW062), an absorption axis 2 of the polarizing plate 1, and a polarizing plate 1 side alignment direction 11 of the liquid crystal layer 4 in the optical film 13. The circularly polarizing plate 14 was produced by pasting together via an acrylic pressure-sensitive adhesive so as to be 5 degrees. In this case, the alignment direction 12 of the liquid crystal molecules on the side opposite to the polarizing plate 1 of the liquid crystal layer 4 in the optical film 13 is 60 degrees. At the time of bonding, the optical film 13 was laminated so that the liquid crystal layer 4 side was in contact with the polarizing plate 1. FIG. 25 shows a schematic diagram of a cross-sectional structure of the polarizing plate 1 and the liquid crystal layer of the optical film 13 in the laminated state. The nematic hybrid structure is the reverse of the case of Example 1, and the liquid crystal layer 4 in the optical film 13 has a surface on which the liquid crystal molecules lie more on the side of the polarizing plate 1 and a surface on which the liquid crystal molecules stand more. On the opposite side to the polarizing plate 1.
The obtained circularly polarizing plate 14 was attached to a transparent glass substrate of an organic EL element of a commercially available organic EL display in the same manner as in Example 1 via an acrylic pressure-sensitive adhesive, and the organic EL display device of the present invention was attached. Created. 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.
In addition, FIG. 26 and Table 2 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident by EZ-CONTRAST and the front reflectance.

(Comparative Example 1)
The optical film (liquid crystal film / adhesive layer / TAC) was the same as in Example 1 except that the drying conditions after coating the coating film were dried at a pressure of 1013 hPa and a temperature of 72 ° C. for 2 minutes, and then rapidly cooled to room temperature. )
When measuring the wavelength dispersion characteristic of retardation (Δn · d) in the front direction of the optical film and the average tilt angle by measuring the phase difference in the oblique direction, Δn · d at a wavelength of 550 nm is 138 nm, and the average tilt angle is 0. It was found to be homogeneous and homogeneously oriented.
The wavelength dispersion characteristics of birefringence are Δn · d (500) / Δn · d (550) = 0.96, Δn · d (580) / Δn · d (550) = 1.02, Δn · d (600) / Δn · d (550) = 1.03, which coincided with the graph of the optical film produced in Example 1 (FIG. 16).

<Antireflection performance evaluation of organic EL display>
For the optical film produced in Comparative Example 1, the orientation direction 5 of the commercially available polarizing plate 1 (manufactured by Sumitomo Chemical Co., SRW062), the absorption axis 2 of the polarizing plate 1 and the liquid crystal layer 4 in the optical film 15 is 45 degrees. In this manner, the circularly polarizing plate 16 was produced by pasting together through an acrylic adhesive. At the time of bonding, the layers were laminated so that the TAC 6 side was in contact with the polarizing plate 1. FIG. 27 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 1 and the liquid crystal layer 4 of the optical film 15.
The obtained circularly polarizing plate 16 was attached to a transparent glass substrate of an organic EL element of a commercially available organic EL display in the same manner as in Example 1 via an acrylic adhesive, and the organic EL display device of the present invention was attached. Created. 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.
Further, Table 2 and Table 2 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident by EZ-CONTRAST and the front reflectance. When comparing Example 1 and Comparative Example 1, it can be seen that Example 1 is superior in viewing angle characteristics of reflectance. Since the wavelength dispersion characteristics of birefringence are the same, this difference in characteristics is thought to be due to the difference in liquid crystal alignment between nematic hybrid alignment and homogeneous alignment, and nematic hybrid alignment is effective in improving the viewing angle of antireflection performance. Suggests that.
In addition, when compared with Example 2, Example 3, Example 4 and Comparative Example 1, all the three examples are excellent in viewing angle characteristics of reflectance, so the structure of nematic hybrid orientation is turned upside down. It can be seen that even when the twisted structure is added to the nematic hybrid alignment, or when two layers of the nematic hybrid alignment are provided, the viewing angle can be improved.

(Comparative Example 2)
An optical film (liquid crystal film / adhesive layer / TAC) was obtained in the same manner as in Example 1 except that the dichroic dye was not mixed. FIG. 29 summarizes the birefringence wavelength dispersion characteristics of the liquid crystal film layer, and Table 1 summarizes the optical characteristics results.
When measuring the wavelength dispersion characteristics of retardation (Δn · d) in the front direction of the optical film and the average tilt angle by measuring the phase difference in the oblique direction, Δn · d at a wavelength of 550 nm is 138 nm, and the average tilt angle is 34. Of a nematic hybrid alignment film of the same degree.
Further, the birefringence wavelength dispersion characteristic of the liquid crystal film layer was measured. FIG. 29 summarizes the birefringence wavelength dispersion characteristics of the liquid crystal film layer, and Table 2 summarizes the optical characteristics results. The wavelength dispersion characteristics of birefringence are Δn · d (500) / Δn · d (550) = 0.98, Δn · d (580) / Δn · d (550) = 1.01, and Δn · d. It was found that d (600) / Δn · d (550) = 1.01, which was inferior to the ideal wavelength dispersion characteristic of the optical film produced in Example 1.

<Antireflection performance evaluation of organic EL display>
The obtained optical film was bonded to a commercially available polarizing plate 1 (manufactured by Sumitomo Chemical Co., Ltd., SRW062) in the same manner as in Example 1. The schematic diagram of the cross-sectional structure of the polarizing plate 1 and the liquid crystal layer 4 of the optical film 3 in the laminated state is the same as FIG. 18 as in Example 1, and the liquid crystal layer in the optical film 3 is a surface on which liquid crystal molecules rise more. Becomes the side of the polarizing plate 1, and the surface on which the liquid crystal molecules lie is opposite to the side of the polarizing plate 1.
The obtained circularly polarizing plate 7 was stuck on a transparent glass substrate of an organic EL element of a commercially available organic EL display via an acrylic pressure-sensitive adhesive to produce the organic EL display device of the present invention. As a result, it was found that an organic EL display device that exhibits a significant effect of preventing external light reflection and has excellent visibility as compared with the case where the circularly polarizing plate 7 is not disposed can be obtained.
In addition, FIG. 30 and Table 2 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident with EZ-CONTRAST and the front reflectance. As a result, the antireflection effect could be confirmed as compared with the case where no circularly polarizing plate was arranged, but it was found that the antireflection effect was inferior compared with Example 1 because of being bluish. This is because the birefringence wavelength dispersion characteristic is not ideal as compared with Example 1, and thus the reflectance deteriorates as a whole. From this, it can be seen that the effect of improving the viewing angle characteristics by the nematic hybrid structure can be obtained, but addition of a dichroic dye is essential for improving the front reflectance.

(Comparative Example 3)
A nematic hybrid alignment liquid crystal film having Δn · d at a wavelength of 550 nm of 138 nm and an average tilt angle of 34 degrees was prepared by the liquid crystal material and the manufacturing method described in Example 1 of JP-A-10-186356. FIG. 31 summarizes the birefringence wavelength dispersion characteristics of the liquid crystal film layer, and Table 1 summarizes the optical characteristics results. Δn · d (500) / Δn · d (550) = 1.05, Δn · d (580) / Δn · d (550) = 0.98, and Δn · d (600) / Δn · d. (550) = 0.97, confirming that it has a “positive dispersion” characteristic in the visible light region.
In the same manner as in Example 1, it was bonded to a polarizing plate and adhered to an organic EL display. When viewed from the front, it was strongly bluish, and the antireflection performance was found to be significantly inferior to that of Example 1. This is considered because the birefringence wavelength dispersion characteristic of the liquid crystal film having a nematic hybrid alignment structure is insufficient.
Further, FIG. 32 shows the results of measuring the viewing angle characteristics of the reflectance when external light is incident by EZ-CONTRAST. Although the effect of improving the viewing angle characteristics by the nematic hybrid structure was confirmed, the reflectance was deteriorated as a whole due to the inferior birefringence wavelength dispersion characteristics.
From the above, it was confirmed that the liquid crystal film having a nematic hybrid structure containing a dichroic dye has a significant improvement effect in the front and oblique directions as the antireflection performance of the organic EL display.

Further, based on the above results, the difference in retardation ratio between the system in which the dichroic dye was mixed (Example 1) and the system in which the dichroic dye was not mixed (Comparative Example 2), that is, formula:
Δna · da (580) / Δna · da (550) −Δnb · db (580) / Δnb · db (550)
The value calculated from is 0.01, which is larger than 0, and it was found that the above formula (1) was satisfied.

(Example 5)
The liquid crystal film produced in Example 1 was incorporated into a polarizing plate reflective liquid crystal display device and evaluated. From the observation side, the configuration is polarizing plate / liquid crystal film prepared in Example 1 / glass substrate / ITO transparent electrode / alignment film / twist nematic liquid crystal / alignment film / metal electrode / reflection film / glass substrate. The adhesive layer between each layer is omitted. The color was evaluated visually by setting the bonding angle so as to display white when the voltage was turned off. In particular, it was confirmed that there was little coloration in black display when the voltage was turned on, thereby providing high contrast and excellent visibility.

1: Polarizing plate 2: Absorption axes 3, 9, 13, 15 of polarizing plate: Optical film 4: Liquid crystal layer 5: Tilt direction 6: TAC films 7, 8, 10, 14, 16: Circularly polarizing plate 11: Liquid crystal alignment Direction (polarizing plate side)
12: Liquid crystal alignment direction (TAC film side)

Claims (10)

The birefringence Δn is a phase difference plate having 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,
Comprising a liquid crystal film comprising a polymerizable liquid crystal composition and at least one dichroic dye, and a liquid crystal compound having a nematic hybrid orientation;
The polymerizable liquid crystal composition includes a rod-shaped liquid crystal compound and a liquid crystal compound having two or more mesogenic groups,
The maximum absorption wavelength of the dichroic dye is in the measurement wavelength region of 380 to 780 nm,
A retardation plate in which the retardation ratio in the normal direction of the retardation plate at a specific wavelength satisfies the following mathematical formulas (2) and (3).
0.80 <Δn · d (500) / Δn · d (550) <1.00 (2)
1.00 <Δn · d (600) / Δn · d (550) <1.15 (3)
(Here, retardation is represented by the product of birefringence Δn and the film thickness d of the retardation plate, and Δn · d (500), Δn · d (550), and Δn · d (600) are respectively wavelengths. Retardation of retardation plate at 500 nm, 550 nm, and 600 nm.) Retardation in the normal direction of the retardation plate is Δna · da,
Retardation in the normal direction of a retardation film composed of a liquid crystal film obtained by removing the dichroic dye from the liquid crystal film is Δnb · db,
When the following formula (1):
Δna · da (580) / Δna · da (550) −Δnb · db (580) / Δnb · db (550)> 0 (1)
(Here, the retardation is represented by the product of birefringence Δn and the thickness d of the retardation plate, and Δna · da (580) and Δna · da (580) are retardations of each retardation plate at a wavelength of 580 nm). Δna · da (550) and Δna · da (550) are retardations of each phase difference plate at a wavelength of 550 nm.)
The retardation plate according to claim 1 , wherein The liquid crystal compound is a liquid crystal film obtained by twisted nematic hybrid orientation, a retardation plate according to claim 1 or 2. The liquid crystal film is a nematic hybrid alignment of a mixture containing a polymerizable liquid crystal composition and at least one dichroic dye in a liquid crystal state, and the alignment is fixed by a crosslinking reaction by light or heat. The phase difference plate according to claim 1 or 2 . The liquid crystal film is obtained by twisting nematic hybrid alignment of a mixture containing a polymerizable liquid crystal composition and at least one dichroic dye in a liquid crystal state, and fixing the alignment by light or heat crosslinking reaction. The phase difference plate according to claim 1 or 2 . The maximum absorption wavelength maximum wavelength and the dichroic dye of the emission spectrum of the display device are different, a phase difference plate according to any one of claims 1-5. The phase difference plate as described in any one of Claims 1-6 whose average tilt angle of the liquid crystal molecule of the said liquid-crystal film is 5-45 degree | times. The liquid crystal twist angle of the film plane of the liquid crystal molecules of the film is 0 to 70 degrees, the phase difference plate according to any one of claims 1-7. A laminated polarizing plate comprising the retardation plate according to any one of claims 1 to 8 and a polarizer. The display apparatus provided with the phase difference plate as described in any one of Claims 1-8 .

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