JP2016188960A - Retardation plate, laminated polarizing plate using retardation plate, and display device using retardation plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a retardation plate having desired birefringent wavelength dispersion characteristics and improved reflective viewing field angle characteristics while minimizing reduction in the transmittance, a laminated polarizing plate using the retardation plate, and a display device having a wide viewing angle using the retardation plate.SOLUTION: The retardation plate has such negative dispersion characteristics that a birefringence Δn increases with the longer measurement wavelength in at least a partial wavelength region of a visible light region. The retardation plate is composed of a liquid crystal film comprising a polymerizable liquid crystal composition and at least one dichroic dye, in which a liquid crystal compound has a nematic hybrid alignment; and the retardation plate satisfies |θ|≥10, where θ represents an angle that maximizes T(θ) defined below. T(θ) represents a transmittance (%) when light is incident to a surface of the liquid crystal film in a direction tilted at the angle θ (degrees) opposite to the tilt direction of the liquid crystal with respect to the normal direction of the liquid crystal film surface, within a plane parallel to both the normal direction of the liquid crystal film surface and the tilt direction.SELECTED DRAWING: Figure 18

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, an organic electroluminescence display device and the like 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 of liquid crystal display devices and viewing angle improving films. Is used in many applications such as a reflection type polarizing plate for reflecting only the right or left-handed circularly polarized light composed of cholesteric liquid crystal or the like. Retardation plate is a plate obtained by cutting a thin inorganic material (calcite, mica, crystal), a film obtained by stretching a polymer film having a high intrinsic birefringence, a rod-like or disk-like liquid crystal composition, and fixing the alignment in the liquid crystal state. A film 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 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, organic electroluminescence (Organic EL) A quarter-wave plate used in an antireflection film for a display device has a measurement wavelength (λ) of 400 to 780 nm, particularly 400 to 700 nm, which is a visible light region. Needs to be converted to linearly polarized light. If this is to be realized with a single phase difference plate, the phase difference may be a quarter wavelength of the measurement wavelength, that is, λ / 4 (nm) at a measurement wavelength of 400 to 780 nm, particularly 400 to 700 nm. Is ideal.

  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-shaped molecule is the two refractive indexes ne and no (ne is an “abnormal refractive index” in a direction parallel to the long molecular axis, and no is “Normal 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), which varies at different speeds depending on the wavelength, and is shown in FIG. Thus, due to the fact that ne changes more rapidly than no toward the short 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. When an extraordinary ray refractive index ne1 and an ordinary ray refractive index no1 of an organic polymer having “positive birefringence” (denoted by rod-like molecule 1 in FIG. 5), birefringence Δn1 (= ne1−no1)> 0. . When an extraordinary ray refractive index ne2 and an ordinary ray refractive index no2 of an organic polymer having “negative birefringence” (denoted by the discotic molecule 3 in FIG. 5), Δn2 (= ne2−no2) <0. Here, in the case of combining materials in which the birefringence Δn1 of the organic polymer having “positive birefringence” is larger than the birefringence Δn2 of the organic polymer having “negative birefringence” (that is, Δn1> Δn2) Case), the total birefringence Δn = Δn1 + Δn2> 0, and the mixture is “positive birefringence”. Further, the chromatic dispersion characteristic D1 of the birefringence Δn1 of the organic polymer having “positive birefringence” is expressed as D1 = Δn1 (450) / Δn1 (650) (where Δn1 (450) and Δn1 (650) are The birefringence of the polymer film at the measurement wavelengths of 450 nm and 650 nm, respectively.), And the wavelength dispersion characteristic D2 of the birefringence Δn2 of the organic polymer having “negative birefringence”, D2 = Δn2 (450) / Δn2 ( 650) (where Δn2 (450) and Δn2 (650) are the birefringence of the polymer film at the measurement wavelengths of 450 nm and 650 nm, respectively), as shown in FIG. 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 can be obtained.

  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 approximate the ideal chromatic dispersion curve in the wide-band region of the measurement wavelength 400 to 700 nm, which is the visible light region, the curve on the short wavelength side is maintained in a state close to the ideal straight line, while another method is used. An attempt to bring the wavelength curve closer to the ideal straight line is required.
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 is greatly deviated from circularly polarized light, narrowing the viewing angle of the display in a liquid crystal display device, or light leakage in an oblique direction in an antireflection film in an 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) (wherein nx and ny represent in-plane main refractive indexes 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 having a wavelength 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

  An object of the present invention has been made in view of the above-mentioned present situation, and has a desired birefringence wavelength dispersion characteristic while minimizing a decrease in transmittance, and has improved reflection viewing angle characteristics, and It is to provide a laminated polarizing plate using a retardation plate and a display device having a wide viewing angle 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. In the retardation plate, the asymmetry degree of light absorption represented by a specific formula of the retardation plate comprising a liquid crystal film containing a nematic hybrid aligned liquid crystal compound and at least one dichroic dye. It has been found that the above technical problem can be solved by making the ratio larger than 1. The present invention has been completed based on such findings.

That is, according to the present invention,
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,
The retardation plate comprises 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 alignment;
Θ that maximizes T (θ) defined below is the following formula (1):
| Θ | ≧ 10 (1)
{T (θ): In a plane parallel to both the normal direction and the tilt direction to the surface of the liquid crystal film, an angle θ () opposite to the tilt direction with respect to the normal direction to the surface of the liquid crystal film. Transmittance) when light is incident on the surface of the liquid crystal film from a direction inclined in degrees)
A phase difference plate satisfying the above is provided.

In the retardation plate according to the present invention, the retardation plate is represented by the following mathematical formula (2):
| T (−θ) −T (θ) |> | T ₀ (−θ) −T ₀ (θ) | (2)
{In the formula, T ₀ (θ): Method to the surface of the liquid crystal film in a plane parallel to both the normal direction and the tilt direction to the surface of the film obtained by removing the dichroic dye from the liquid crystal film Transmittance (%) when light is incident on the surface of the liquid crystal film from a direction inclined at an angle θ (degrees) opposite to the tilt direction with respect to the linear direction
θ (degrees): represents a numerical value in the range of 10 to 40}
May be satisfied.

In the retardation plate according to the present invention, the ratio of retardation in the normal direction of the retardation plate at a specific wavelength is expressed by the following mathematical formulas (3) and (4):
0.80 <Δn · d (500) / Δn · d (550) <1.00 (3)
1.00 <Δn · d (600) / Δn · d (550) <1.15 (4)
(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)
May be satisfied.

In the phase difference plate according to the present invention, retardation in the normal direction of the phase difference 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 (5)
Δna · da (580) / Δna · da (550) −Δnb · db (580) / Δnb · db (550)> 0 (5)
(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.)
May be satisfied.

  In the retardation plate according to the present invention, the maximum absorption wavelength of the dichroic dye may be in a wavelength region of 380 to 780 nm.

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

  In the retardation plate according to the present invention, an average tilt angle of liquid crystal molecules of the liquid crystal film may be 10 degrees to 45 degrees.

  According to this invention, the laminated polarizing plate provided with the said phase difference plate and polarizer is provided.

  According to this invention, the display apparatus provided with the said phase difference plate is provided.

  According to the present invention, in the phase difference 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 range of the visible light range, the phase difference plate is polymerized. A retardation plate comprising a liquid crystal film comprising a liquid crystal composition and at least one dichroic dye, wherein the liquid crystal compound has a nematic hybrid orientation, and satisfying a specific relational expression regarding transmittance. Can do. A retardation plate satisfying such a specific relation and having a phase difference of 1/4 wavelength at a measurement wavelength of 550 nm is a circularly polarized light and a linearly polarized light is circularly polarized in a wide wavelength region in the front and oblique directions. Since it functions as a phase difference plate that converts to polarized light, if used in a liquid crystal display device, display characteristics such as brightness and contrast ratio are improved in the front and particularly in an oblique direction, and if used in an organic electroluminescence display device, it is a specular reflection. The high prevention performance against 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. FIG. 4 is a diagram showing wavelength dispersion characteristics of birefringence Δn of the liquid crystal film produced in Example 1. 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. FIG. 4 is a diagram showing the transmittance of the liquid crystal film produced in Example 1. It is a figure which shows the layer structure of the circularly-polarizing plate produced in Examples 1-3 and Comparative Examples 1-3. 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. 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 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. 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 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 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. However, it comprises a liquid crystal film containing a polymerizable liquid crystal 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 retardation 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 between the slopes of the short wavelength side curve and the long wavelength side curve from 550 nm which is the central wavelength of visible light. There is a tendency. Therefore, in order to approximate the ideal chromatic dispersion curve in the wide-band region of the measurement wavelength 400 to 700 nm, which is the visible light region, the curve on the short wavelength side is maintained in a state close to the ideal straight line, while another method is used. An attempt to bring the wavelength curve closer to the ideal straight line is required. 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 a liquid crystal film having birefringence having “negative dispersion” characteristics, “negative dispersion” characteristics in birefringence may be inferior in the long wavelength region, and dichroism having an anomalous dispersion region. By adding a dye, a long wavelength region can be improved, and a retardation plate 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 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),
0.80 <Δn · d (500) / Δn · d (550) <1.00 (3) and 1.00 <Δn · d (600) / Δn · d (550) <1.15 (4) 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 (3-1)
And 1.02 <Δn · d (600) / Δn · d (550) <1.10 (4-1)
It is. When deviating from these values, for example, when used as a quarter wave plate, when linearly polarized light of 400 to 700 nm is incident on this film, the polarization state obtained is a perfect circle at a specific wavelength. Although polarized light can be obtained, there is a problem that it is greatly deviated from circularly polarized light at other wavelengths.

  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, it is preferable to satisfy the following formula (5).
Δna · da (580) / Δna · da (550) −Δnb · db (580) / Δnb · db (550)> 0 (5)
(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 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 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.

In the liquid crystal film, θ which maximizes T (θ) defined below is expressed by the following formula (1):
| Θ | ≧ 10 (1)
{T (θ): In a plane parallel to both the normal direction and the tilt direction to the surface of the liquid crystal film, an angle θ () opposite to the tilt direction with respect to the normal direction to the surface of the liquid crystal film. Degree) when the light is incident on the surface of the liquid crystal film. In the liquid crystal film, θ that maximizes T (θ) preferably satisfies 50 ≧ | θ | ≧ 15, and more preferably satisfies 40 ≧ | θ | ≧ 20. Satisfying the above formula (1) means that the light incident at the incident angle θ (degrees) is larger than the light incident at the incident angle 0 (degrees) and is incident at the incident angle −θ (degrees). Is smaller than the absorbance of incident light at an incident angle of 0 (degrees), indicating that the angle at which the absorbance of light is minimized deviates from 0 degrees. That is, the addition of the dichroic dye shifts the angle at which the light absorbance is minimized from 0 degrees, thereby producing “asymmetric” light absorption. When the absorbance of the liquid crystal film satisfies the above formula (1), the reflection viewing angle characteristics can be improved.

Further, the retardation plate has the following formula (2):
| T (−θ) −T (θ) |> | T ₀ (−θ) −T ₀ (θ) | (2)
{In the formula, T ₀ (θ): Method to the surface of the liquid crystal film in a plane parallel to both the normal direction and the tilt direction to the surface of the film obtained by removing the dichroic dye from the liquid crystal film Transmittance (%) when light is incident on the surface of the liquid crystal film from a direction inclined at an angle θ (degrees) on the other side opposite to the liquid crystal compound inclined to one side with respect to the linear direction
θ (degrees): a numerical value in the range of 10-40, preferably a numerical value in the range of 25-35, for example representing 25, 30, or 35}
It is preferable to satisfy. Satisfying the above formula (2) means that the difference between the absorbance of light incident at an incident angle θ (degrees) and the absorbance of light incident at an incident angle −θ (degrees) increases before and after the addition of the dichroic dye. Indicates that That is, by adding a dichroic dye, light incident at an incident angle θ (degrees) absorbs more light than incident light at an incident angle −θ (degrees), resulting in “asymmetry” of light absorption. It shows that. When the absorbance of the liquid crystal film satisfies the above formula (2), the reflection viewing angle characteristics can be improved.

  FIG. 14 shows a cross-sectional structure of a liquid crystal film including the nematic hybrid aligned liquid crystal compound of the present invention. Further, FIG. 14 shows the incident angle θ (degrees) of light incident from the vertical direction of the liquid crystal compound with respect to the normal of the surface of the liquid crystal film, and the liquid crystal compound with respect to the normal of the surface of the liquid crystal film. The incident angle θ (degree) (incident angle−θ (degree)) of light incident from the horizontal direction is shown. Here, in the liquid crystal film including the liquid crystal compound with nematic hybrid alignment, the director of the liquid crystal compound is oriented at different angles at all locations in the film thickness direction of the liquid crystal film. Therefore, 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. Note that the tilt direction (axis) of the liquid crystal film is a component projected onto the c-plane of the liquid crystal molecule director and the director when the c-plane is viewed from the b-plane side 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).

  In a liquid crystal film comprising a liquid crystal compound with nematic hybrid alignment, the angle between the director of the liquid crystal molecules and the film plane in the vicinity of one film interface of the liquid crystal film is preferably 20 to 90 degrees, more preferably as an absolute value. Is 30 to 70 degrees, and in the vicinity of the film interface opposite to the film surface, the angle is preferably 0 to 50 degrees, more preferably 0 to 30 degrees as an absolute value. The average tilt angle in the alignment structure is preferably 5 to 40 degrees as an absolute value, more preferably 10 to 35 degrees, and most preferably 15 to 30 degrees. If the average tilt angle is within the above numerical range, the reflection 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.

In addition, the retardation plate of the present invention may be a liquid crystal film including a twisted nematic hybrid aligned liquid crystal compound. A liquid crystal film comprising a twisted nematic hybrid aligned liquid crystal compound 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, a liquid crystal film comprising a twisted nematic hybrid aligned liquid crystal compound has a film thickness direction in which the director of the liquid crystal molecules twists from one surface to the other while the optical anisotropic axis is twisted in the in-plane direction. The film is inclined at different angles. The twist angle in the alignment structure is preferably 0 to 70 degrees as an absolute value, more preferably 0 to 60 degrees, and most preferably 0 to 59 degrees. If the twist angle is within the above numerical range, the display characteristics when viewed from the front, such as contrast and antireflection performance, can be improved when the liquid crystal display device or organic EL display device is combined with a polarizing plate. it can. 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 suppressed 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 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.

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.

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. Moreover, if content of a dichroic pigment | dye is 50 weight part 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 weight 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.
The polymerizable liquid crystal composition is not particularly limited as long as it contains a liquid crystal compound capable of fixing the alignment state by polymerization. The polymerizable liquid crystal composition in the present invention includes a liquid crystal compound having one or more polymerizable groups (polymerizable liquid crystal compound), a liquid crystal compound having no polymerizable group, and a polymerizable compound not exhibiting liquid crystallinity. A mixture of a liquid crystal compound having a polymerizable group and a polymerizable compound not exhibiting liquid crystallinity, and a mixture of a liquid crystal compound having a polymerizable group and a liquid crystal compound having no polymerizable group. There may be.

  In the present invention, known polymerizable liquid crystal compounds 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%. When 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. When 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, it is preferable that the phase difference Δn · d satisfies the above formulas (3) and (4). Particularly, as a method of satisfying the above formula (3), two or more kinds of polymerizable liquid crystal compounds are used. A compound having a mesogenic group, in which at least one mesogenic group is aligned in a direction substantially orthogonal to the slow axis of the parallel (homogeneous) alignment of the liquid crystal layer, so that the phase difference increases as the wavelength increases. Are described in JP 2002-267838 A and JP 2010-31223 A. 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.

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 (polymerizable monomer) 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 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 addition amount of such other polymerizable monomers is preferably 0.5 to 50% by weight based on the total amount of the liquid crystal compound having a polymerizable group and other polymerizable monomers not exhibiting liquid crystallinity. 1 to 30% by weight is preferable. 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.

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)
A suitable photopolymerization initiator (trade name “UVI6974”) manufactured by Carbide 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 for producing the retardation plate is not particularly limited. For example, a composition containing a polymerizable liquid crystal composition, a dichroic dye, and various compounds added as necessary is melted. Alternatively, a coating film is formed by applying a solution of the composition onto an alignment substrate. Next, the coating film is dried, heat-treated (liquid crystal alignment), or nematic hybrid alignment using means for fixing the alignment such as light irradiation and / or heat treatment (polymerization / crosslinking) as necessary. By fixing the liquid crystal film, a liquid crystal film in which the orientation of the liquid crystal and the dichroic dye is fixed is formed.

  In this specification, the alignment state “fixed in the state of nematic hybrid alignment” means that in the liquid crystal film obtained by polymerizing the polymerizable liquid crystal composition and fixing the alignment of the liquid crystal compound, the nematic hybrid Derived from the polymerizable liquid crystal compound or the like, which means that the orientation (the orientation in which the directors of the liquid crystal molecules are seen from the film thickness direction of the film (preferably the orientation aligned at different angles in all places) is confirmed. (Preferably 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, and the like). Any one of them may be fixed in a nematic hybrid orientation state.In this specification, “nematic hive” Tsu and de structure "refers to the alignment structure in which a liquid crystal compound in the liquid crystal film is a nematic hybrid orientation.

  The solvent used for preparing the solution is not particularly limited as long as it can dissolve the liquid crystal composition and the dichroic dye and can be distilled off under suitable conditions. For example, propylene glycol from the viewpoint of drying speed suitable for applying the solution so as to obtain a uniform film thickness, ease of handling (harmful to the environment) and solubility in polymerizable liquid crystal compounds and dichroic dyes. 1-monomethyl ether 2-acetate, 2-methoxyethyl acetate, toluene, xylene, methoxybenzene, 1,2-methoxybenzene, cyclohexanone, cyclopentanone, methyl cellosolve, ethyl cellosolve, butyl cellosolve, γ-butyrolactone, 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 the solvent is 30% by weight or more, the amount of the solvent with respect to the mixture of the polymerizable liquid crystal compound and the dichroic dye is secured, so that the precipitation of the liquid crystal during storage can be suppressed, It is possible to suppress a decrease in wettability due to an increase in viscosity, and to perform a good coating during the production of a retardation plate. In addition, if the content of the solvent is 95% by weight or less, when removing the solvent, the removal time (drying time) does not take long, and when the film is produced, the work efficiency is prevented from being lowered, 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.

  Such a substrate is not particularly limited, but in the case where the laminate of the liquid crystal layer and the substrate to be formed is used as it is for an optical film or the like, depending on its use, etc., a retardation function It is good also as what has. Further, such a substrate may be uniaxially stretched (so-called uniaxially stretched film) or biaxially stretched (so-called biaxially stretched film). Such a base material may be used as a film having optical anisotropy by developing biaxial optical anisotropy by stretching the base material in the vertical direction and the horizontal direction.

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

  Some of these films exhibit sufficient alignment ability for the 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 the solution of the liquid crystal composition, 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. When the temperature condition is 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 the drying time is 10 seconds or more, the drying of the solvent is slow, so that 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. When the film thickness is within the above numerical range, the optical performance of the obtained liquid crystal film can be sufficiently exhibited, and the liquid crystal compound and the dichroic dye can be sufficiently oriented.

Next, a method for fixing the orientation will be described.
As a method for fixing the alignment state of the liquid crystal compound by polymerizing the polymerizable liquid crystal composition, a known method capable of polymerization is appropriately employed depending on the type of the polymerizable liquid crystal composition or the polymerization initiator used. can do. 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 during 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 composition and the dichroic dye on the alignment substrate, the solvent is removed from the coating film to align the liquid crystal compound and the dichroic dye, and the liquid crystal By fixing the 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.

  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 the nematic hybrid alignment, a known method can be appropriately adopted, and is not particularly limited. However, a pair of orthogonal polarizing plates (a direction in which one deflector deflects and a direction in which the other deflector deflects) A method for confirming transmitted light with the naked eye 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 in which are perpendicular to each other, You may employ | adopt the method of observing a phase difference plate with a polarizing microscope. Between the pair of orthogonal polarizing plates placed on the backlight, the liquid crystal film is disposed at an angle such that the transmission intensity of light from the backlight when viewed from the front is the darkest, and is slow relative to the surface of the liquid crystal film. The presence of nematic hybrid alignment can be confirmed by confirming that it becomes bright when observed obliquely with the phase axis as the axis and remains dark when observed obliquely with the fast axis as the axis. . 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 vertical incident angle to a specific angle. Using a product name “Axoscan” manufactured by Oji Scientific Instruments, and a product name “KOBRA-21ADH” manufactured by Oji Scientific Instruments Co., Ltd.) in a direction in which the viewing angle increases from 0 degree (perpendicular to the liquid crystal film). The phase difference is measured while appropriately changing the angle, and the phase difference of the sample is obtained for each of a plurality of viewing angles. Based on confirming that the phase difference is confirmed and the phase difference in the direction in which the viewing angle becomes larger with respect to the surface of the liquid crystal film shows that the values of the − and + directions of the viewing angle are asymmetric with each other. Thus, a method for confirming the presence or absence of nematic hybrid alignment may be employed.

  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, dichroic substances such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And a polyene-based oriented film such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product or a polyvinyl chloride dehydrochlorinated product. 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.

  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.

  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 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 this invention does not limit which film surface of a liquid crystal film is a polarizing plate side, it is requested | required for the optical characteristic requested | required of a laminated polarizing plate, a liquid crystal display device provided with the said laminated polarizing plate, and an organic electroluminescent display device. In consideration of display characteristics and the like, it is desirable to determine the configuration of the laminated polarizing plate of the present invention and the arrangement conditions for the liquid crystal display device and the organic EL display device.

<Display device>
The display device of the present invention includes the retardation plate of the present invention. In addition, the display device of the present invention includes a laminated polarizing plate having the function of elliptically polarized light or circularly polarized light provided with 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 image display device is not particularly limited, such as a liquid crystal display device, an organic EL display device, and a plasma display. Such known display devices 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 conventionally known liquid crystal cells.

  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 display 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.
For example, in an organic EL display device including an organic electroluminescent light emitting device including a transparent electrode on the surface side of the organic light emitting layer and a metal electrode on the back surface side of the organic light emitting layer, a polarizing plate is provided on the surface side of the transparent electrode. And a phase difference 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 is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. 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 phase difference plate of the invention is nematic hybrid orientation, it is preferably in the range of 40 to 50 degrees, more preferably 42 to 48 degrees, and still 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 orientation, 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 in the previous period 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) Alignment state of liquid crystal This was confirmed using an Olympus BH2 polarizing microscope.
(2) Refractive index Refractive indexes no and ne are measured using spectroscopic ellipsometry (manufactured by Horiba, Ltd., product name “AUTO-SE”) under conditions of a temperature of 20 ° C. ± 2 ° C. and a relative humidity of 60 ± 5%. A spectrum in the wavelength region of 440 to 1000 nm was measured.
(3) Birefringence and oblique transmittance Measured using an automatic birefringence meter Axoscan manufactured by Axometrics.
(4) Polarization absorption spectrum of dichroic dye Measurement was performed using a spectrum (V-570) manufactured by JASCO Corporation.
(5) Viewing angle of reflectance 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 measuring device EZ-CONTRAST manufactured by ELDIM. The evaluation criteria for the reflection viewing angle characteristics are as follows.
Evaluation (circle): The reflective viewing angle characteristic was favorable.
Evaluation Δ: Reflective viewing angle characteristics were somewhat inferior.
Evaluation x: The reflection viewing angle characteristic was inferior.

[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, and the first mixture (polymerizable liquid crystal composition (A) and Obtained). Next, 0.08 part by weight of a dichroic dye (Nagase Sangyo Trisazo dye, trade name: G-241, maximum absorption wavelength 560 nm) is added to 100 parts by weight of the first mixture, and a polymerization initiator ( Ciba-Geigy, trade name: Irgacure 651, solid at room temperature (25 ° C.)) is 3 parts by weight with respect to 100 parts by weight of the total amount of the polymerizable liquid crystal composition (A) and the dichroic dye. It added by the ratio and the 2nd mixture (solid) formed by mixing a polymeric liquid crystal compound (A), a dichroic dye, and a polymerization initiator was obtained.
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) and A mixed solution (third mixture) containing a chromatic 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, and the polymerization initiator are used. The solvent was used so that the total amount was 33% by weight.

<Preparation of liquid crystal layer>
First, the alignment substrate was prepared as follows. A polyethylene naphthalate (PET) film having a thickness of 38 μm (PEN manufactured by Teijin Limited) was cut into a 15 cm square, and a 5 wt% solution of alkyl-modified polyvinyl alcohol (PVA: MP-203 manufactured by Kuraray Co., Ltd.) A mixed solvent of water and 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.

The alignment substrate thus obtained is coated (coated) with the third mixture obtained as described above by a spin coating method to form a coating film (wet film thickness: 5 μm). And a laminated body of the alignment substrate was obtained.
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 after removing the solvent from the coating film by drying, it was rapidly cooled to room temperature.
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, A laminated body in which a liquid crystal compound is polymerized (cured) to fix an alignment state and a liquid crystal film in which the alignment state is fixed is laminated on an alignment substrate. (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 triacetylcellulose (TAC) film (Fuji Film) is bonded to the obtained liquid crystal layer on the alignment substrate through an ultraviolet curable adhesive. The product was transferred to Z-TAC (40 um). That is, on the cured liquid crystal layer on the PET film, the adhesive was applied to a thickness of 5 μm, laminated with the TAC film, and after the adhesive was cured by irradiating ultraviolet rays from the TAC film side, The alignment substrate was peeled off.
When the obtained optical film (liquid crystal layer / 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 layer and the TAC film alone is measured using “Axoscan”, and the birefringence wavelength dispersion of the liquid crystal film layer is calculated by subtracting both. Characteristics were measured. FIG. 16 summarizes the birefringence wavelength dispersion characteristics of the liquid crystal layer, and Table 1 summarizes the optical characteristics results. Δn · d at 550 nm was 138 nm, and Δn · d (500) / Δn · d (550) = 0.96 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 have a nematic hybrid orientation rather than a uniform tilt orientation by the method described in Examples of JP-A-11-194325. As a result of analysis, the average tilt angle was 26.7 degrees, and the tilt angle at the TAC film side interface was 48.0 degrees.

Subsequently, the angle dependency of the transmittance of the laminate of the TAC film and the liquid crystal was measured using “Axoscan”. As shown in FIG. 14, in a plane parallel to both the normal direction to the surface of the optical film and the tilt direction, an angle θ (in the direction opposite to the tilt direction with respect to the normal direction to the surface of the optical film) The measured value of the transmittance when light is incident on the surface of the optical film from a direction inclined at a degree is expressed as T (θ). When θ is negative, an angle −θ (degrees) in the tilt direction with respect to the normal direction to the surface of the optical film in a plane parallel to both the normal direction to the surface of the optical film and the tilt direction. The measured value of the transmittance when light is incident on the surface of the optical film from the direction inclined at () is expressed as T (θ). At the same time, the angle dependency of the transmittance of the optical film prepared in the same manner except that no dichroic dye was added to the liquid crystal film in the method for preparing the optical film laminate was measured in the same manner (FIG. 18). A measured value of transmittance at an incident angle θ (degrees) of an optical film laminate without adding a dichroic dye at an incident angle θ (degrees) is represented as T ₀ (θ). Further, a measured value of transmittance at an incident angle of −θ (degrees) of an optical film laminate to which no dichroic dye is added at an incident angle of −θ (degrees) is expressed as T ₀ (−θ). As a result of the measurement, the optical film satisfied the above mathematical expressions (1) and (2).

<Antireflection performance evaluation of organic EL display>
With respect to the obtained optical film, a commercially available polarizing plate 1 (manufactured by Sumitomo Chemical Co., Ltd., trade name: SRW062), an absorption axis 2 of the polarizing plate 1 and a tilt direction 5 of the liquid crystal layer 4 in the optical film 3 become 45 degrees. In this manner, the circularly polarizing plate 7 was produced by pasting together through an acrylic 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. 19 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. 20 and Table 1 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident 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 1. It was confirmed that

[Example 2]
In the same manner as in Example 1 except that the amount of the dichroic dye added was 0.20 parts by weight with respect to 100 parts by weight of the first mixture, an optical film (liquid crystal layer / adhesive layer / TAC). The average tilt angle of the liquid crystal film was 30.8 degrees, and the tilt angle at the interface on the TAC film side was 56.2 degrees. Moreover, the optical film satisfy | filled the said Numerical formula (1) and (2).
An organic EL display device of the present invention was produced from the obtained optical film in the same manner as in Example 1. FIG. 21 and Table 1 show the results of measuring the viewing angle characteristics of the reflectance when incident external light is incident using a reflection viewing angle measuring device EZ-CONTRAST manufactured by ELDIM and the front reflectance.

[Example 3]
In the same manner as in Example 1 except that the amount of the dichroic dye added was 0.05 parts by weight with respect to 100 parts by weight of the first mixture, an optical film (liquid crystal layer / adhesive layer / TAC). The average tilt angle of the liquid crystal film was 24.3 degrees, and the tilt angle of the TAC side interface was 45.0 degrees. Moreover, the optical film satisfy | filled the said Numerical formula (1) and (2).
An organic EL display device of the present invention was produced from the obtained optical film in the same manner as in Example 1. FIG. 22 and Table 1 show the viewing angle characteristics of the reflectance and the front reflectance when external light is incident.

[Comparative Example 1]
An optical film (liquid crystal layer / adhesive layer / TAC) was obtained in the same manner as in Example 1 except that no dichroic dye was added. The average tilt angle of the liquid crystal layer was 18.2 degrees, and the tilt angle of the interface on the TAC film side was 32.0 degrees. Moreover, the optical film did not satisfy | fill said Numerical formula (1) and (2).
An organic EL display device of the present invention was produced from the obtained optical film in the same manner as in Example 1. FIG. 23 and Table 1 show the viewing angle characteristics of the reflectance and the front reflectance when external light is incident. It turned out that Examples 1-3 have a low front reflectance compared with the comparative example 1, and show a high antireflection effect.

[Comparative Example 2]
The optical film (liquid crystal layer / adhesive) was the same as in Example 1 except that the drying conditions after the coating was applied were pressure: 1013 hPa, temperature: dried at 72 ° C. for 2 minutes, and then rapidly cooled to room temperature. Layer / TAC). The average tilt angle of the liquid crystal layer was 0.8 degrees, the tilt angle of the interface on the TAC film side was 1.4 degrees, and it was found that the alignment was homogeneous. Moreover, the optical film did not satisfy | fill said Numerical formula (1) and (2).
An organic EL display device of the present invention was produced from the obtained optical film in the same manner as in Example 1. FIG. 24 and Table 1 show the viewing angle characteristics of the reflectance and the front reflectance when external light is incident. It was found that Example 1 has the same front reflectance as Comparative Example 2, but has significantly higher reflection viewing angle characteristics.

[Comparative Example 3]
The optical film (liquid crystal layer / adhesive layer / TAC) was prepared in the same manner as in Comparative Example 2 except that the amount of the dichroic dye added was 0.2 parts by weight with respect to the total amount of 100 parts by weight. Obtained. The average tilt angle of the liquid crystal layer was 0.6 degrees, the tilt angle of the interface on the TAC film side was 1.0 degree, and it was found that the liquid crystal layer was homogeneously aligned. Moreover, the optical film did not satisfy | fill said Numerical formula (1) and (2).
An organic EL display device of the present invention was produced from the obtained optical film in the same manner as in Example 1. FIG. 25 and Table 1 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. It was found that Example 2 has the same front reflectance as Comparative Example 3, but has significantly higher reflectance viewing angle characteristics.

1: Polarizing plate 2: Absorption axis of polarizing plate 3: Optical film 4: Liquid crystal layer 5: Tilt direction 6: TAC film 7: Circular polarizing plate

Claims (9)

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,
The retardation plate comprises 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 alignment;
Θ that maximizes T (θ) defined below is the following formula (1):
| Θ | ≧ 10 (1)
{T (θ): In a plane parallel to both the normal direction and the tilt direction to the surface of the liquid crystal film, an angle θ () opposite to the tilt direction with respect to the normal direction to the surface of the liquid crystal film. Transmittance) when light is incident on the surface of the liquid crystal film from a direction inclined in degrees)
Satisfying the retardation plate. The retardation plate has the following formula (2):
| T (−θ) −T (θ) |> | T ₀ (−θ) −T ₀ (θ) | (2)
{In the formula, T ₀ (θ): Method to the surface of the liquid crystal film in a plane parallel to both the normal direction and the tilt direction to the surface of the film obtained by removing the dichroic dye from the liquid crystal film Transmittance (%) when light is incident on the surface of the liquid crystal film from a direction inclined at an angle θ (degrees) opposite to the tilt direction with respect to the linear direction
θ (degrees): represents a numerical value in the range of 10 to 40}
The retardation plate according to claim 1, wherein The ratio of retardation in the normal direction of the phase difference plate at a specific wavelength is expressed by the following mathematical formulas (3) and (4):
0.80 <Δn · d (500) / Δn · d (550) <1.00 (3)
1.00 <Δn · d (600) / Δn · d (550) <1.15 (4)
(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 phase difference plate according to claim 1 or 2, satisfying 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 (5)
Δna · da (580) / Δna · da (550) −Δnb · db (580) / Δnb · db (550)> 0 (5)
(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 phase difference plate according to claim 1, wherein   The phase difference plate according to claim 1, wherein the maximum absorption wavelength of the dichroic dye is in a wavelength region of 380 to 780 nm.   The phase difference plate according to claim 1, wherein a maximum absorption wavelength of the dichroic dye is different from a maximum wavelength of an emission spectrum of the display device.   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 10 to 45 degree | times.   A laminated polarizing plate comprising the retardation plate according to any one of claims 1 to 7 and a polarizer.   The display apparatus provided with the phase difference plate as described in any one of Claims 1-7.