JP2017037150A - Phase difference plate, lamination polarizing plate using phase difference plate, and display using phase difference plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase difference plate formed of a liquid crystal film that has a "negative dispersion" property closer to the ideal while maintaining high transmittance.SOLUTION: There is provided a phase difference film that has a "negative dispersion" property in which birefringence Δn increases as the measurement wavelength increases in at least part of a wavelength area in a visible light area, wherein the phase difference plate is formed of a liquid crystal film including a polymerizable liquid crystal composition including a liquid crystal compound and a dichromatic pigment; the liquid crystal compound is fixed in nematic hybrid alignment in the liquid crystal film; the order parameter (S) of the dichromatic pigment in the phase difference plate represented by the following formula (1) is in a range of 1.0≥S≥0.5. (1): S=(DR-1)/(DR+2)(1), wherein DR is the dichroic ratio of the dichromatic pigment.SELECTED DRAWING: Figure 11

Description

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

  The phase difference plate is an optical member 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, viewing angle improvement applications, a polarizing plate and a quarter wave plate. Further, it is used in many applications such as an antireflection film for organic EL display devices and a reflective polarizing plate for reflecting only one of clockwise and counterclockwise circularly polarized light composed of cholesteric liquid crystal. A phase difference plate is a film obtained by thinly cutting an inorganic material (calcite, mica, crystal), a film obtained by stretching a film having a high intrinsic birefringence, a film in which a rod-like or disk-like liquid crystal composition is fixed in the liquid crystal state. It 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 converts linearly polarized light into circularly polarized light, and the half wavelength plate converts the polarization vibration plane of the 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 and antireflection film for organic EL display devices The quarter-wave plate used in is required to convert linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light at a measurement wavelength (λ) of 400 to 780 nm, particularly 400 to 700 nm, in the visible light region. In order to realize this with a single retardation plate, it is ideal that the phase difference is ¼ wavelength of the measurement wavelength, that is, λ / 4 (nm) at the measurement wavelength of 400 to 780 nm, particularly 400 to 700 nm. It is.

  In general, the above-described retardation plate material or the like is used as a quarter-wave plate, but the retardation of these materials has wavelength dependency. Here, the dispersion characteristic is such that the phase difference is larger as the measurement wavelength is shorter, and the phase difference is smaller as the wavelength is longer. The dispersion characteristic is “positive dispersion”, and the phase difference is smaller and longer as the measurement wavelength is shorter. The dispersion characteristic in which the phase difference increases as the value becomes is defined as “negative dispersion”. In general, the birefringence of a film (polymer film) produced using a polymer such as a liquid crystal compound has a “positive dispersion” characteristic. Ideally, it has a “negative dispersion” characteristic for use as a quarter-wave plate. It is difficult to obtain an ideal “negative dispersion” characteristic using a single polymer film. When a polymer film having a “positive dispersion” characteristic is used as a retardation plate, white light is various. Polarized light having a different wavelength is generated, and colored polarized light is generated.

Each publication of Patent Document 1 and Patent Document 2 discloses a retardation plate in which two films containing a liquid crystal compound having optical anisotropy are laminated. The retardation plate described in Patent Document 1 is obtained by bonding a quarter-wave plate and a half-wave plate with their optical axes intersecting. The phase difference plate described in Patent Document 2 is formed by laminating at least two retardation plates having a retardation of 160 to 320 nm so that their slow axes are not parallel to or perpendicular to each other. In Patent Document 3, a birefringence medium having a birefringence index Δn having a wavelength dispersion value α (α = Δn (450 nm) / Δn (650 nm)) of αA <αB is laminated in directions orthogonal to each slow axis. In addition, at least one of the birefringent media is made of a liquid crystal compound in a homogeneously aligned molecular orientation state, the relationship of the phase difference R of each birefringent media is R _A > R _B , and the chromatic dispersion value α is smaller than 1. A laminated retardation plate is disclosed. The retardation plate described in any of the publications is specifically composed of a laminate of two birefringent media.

  By adopting the methods described in the above publications, it is possible to realize a quarter wavelength plate applicable to light in a wide wavelength region. However, in the manufacture of the retardation plate described in each of Patent Document 1 and Patent Document 2, a complicated manufacturing process is required to adjust the optical direction (optical axis and slow axis) of the two polymer films. And The optical direction of the polymer film generally corresponds to the longitudinal or lateral direction of the sheet or roll film. Industrial production of a film having an optical axis and a slow axis in an oblique direction is difficult. In the inventions described in each of Patent Document 1 and Patent Document 2, the optical directions of the two films are set to an angle that is neither parallel nor orthogonal. Therefore, in order to manufacture the retardation film described in each of Patent Document 1 and Patent Document 2, it is necessary to cut two films at a predetermined angle and bond the obtained chips together. Becomes complicated. As a result, problems such as quality deterioration due to shaft misalignment, yield reduction, cost increase, and degradation due to contamination are likely to occur. In addition, it is difficult to strictly adjust the retardation in the production method as described above.

  Patent Document 3 discloses a liquid crystal film made of a rod-like liquid crystal compound as a retardation film that is a thin film and has negative birefringence. The retardation plate described in Patent Document 3 is obtained by homogeneously aligning 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 mesogenic group with respect to the optical axis direction of the rod-like liquid crystal compound. Is oriented in a substantially orthogonal direction to achieve negative birefringence. Since the rod-like liquid crystal compound has a relatively large birefringence Δn as compared with the copolymer film, it can be thinned to a thickness of about several μm.

However, the method of combining the positive birefringent material and the negative birefringent material described in Patent Document 3 makes it difficult to obtain a characteristic in which the phase difference becomes a quarter wavelength over a wide band of 400 to 700 nm, as shown in FIG. The long wavelength side tends to deviate from the ideal straight line. This is due to the fact that the slopes of the shorter wavelength side curve and the longer wavelength side curve than 550 nm which is the center wavelength of visible light are different. Therefore, in order to obtain an ideal chromatic dispersion curve over a wide band of 400 to 700 nm, which is the visible light region, the curve on the long wavelength side is maintained by another method while maintaining the curve on the short wavelength side close to the ideal straight line. It is necessary to try to approximate the ideal straight line.
In addition, the retardation plate described above achieves a quarter-wave plate in a wide wavelength region, so that near-ideal circularly polarized light can be obtained in the light incident from the normal direction of the circularly polarizing plate. The incident light from the light source is converted into elliptically polarized light. When used as a liquid crystal display device, the viewing angle of the display is narrowed, and when used as an antireflection film for an organic EL display device, oblique light leakage occurs. There is a risk.

By the way, Patent Document 4 discloses that a dye such as anthraquinone is added to liquid crystal molecules having no “negative dispersion” characteristics.
Patent Document 5 discloses that a dichroic dye is added as a dye added to a retardation plate made of a liquid crystal compound. Furthermore, Patent Document 6 discloses a polarizing element obtained by adding a dichroic dye to a smectic liquid crystal compound.

  However, when dichroic dyes as described in Patent Documents 4 to 6 are used, it is difficult to suppress the addition amount, and it has a “negative dispersion” characteristic close to ideal while maintaining high transmittance. It has been difficult to realize a retardation plate made of a liquid crystal film.

JP-A-10-68816 JP-A-10-90521 JP 2002-267838 A JP 2009-9062 A JP 2011-178946 A JP 2013-33249 A

  The present inventors have now added a dichroic dye by adding a dichroic dye having a predetermined order parameter (S) to a liquid crystal film containing a polymerizable liquid crystal composition having a “negative dispersion” characteristic. Since a high dichroic ratio was obtained while suppressing the amount, it was found that a retardation plate having a “negative dispersion” characteristic closer to the ideal could be realized while maintaining a high transmittance. The present invention is based on this finding.

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 containing a liquid crystal compound and a dichroic dye, and the liquid crystal compound has a nematic hybrid orientation in the liquid crystal film,
There is provided a retardation plate having an order parameter (S) of the dichroic dye in the retardation plate represented by the following formula (1) in a range of 1.0 ≧ S ≧ 0.5.
S = (DR-1) / (DR + 2) (1)
(In the formula (1), DR represents the following formula (2):
(In the formula (2), λ represents the wavelength (nm) of light in vacuum,
Ae (λ) represents a polarization absorption spectrum parallel to the slow axis in the retardation plate,
Ao (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the retardation plate,
Ae0 (λ) represents a polarization absorption spectrum parallel to the slow axis in the retardation plate excluding the dichroic dye,
Ao0 (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the retardation plate excluding the dichroic dye. The dichroic ratio of the dichroic dye represented by )

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

  In the retardation plate according to the present invention, the content of the dichroic dye is preferably 0.03 to 0.8 parts by weight with respect to 100 parts by weight of the polymerizable liquid crystal composition.

  In the phase difference plate according to the present invention, the maximum absorption wavelength of the dichroic dye is preferably 380 to 780 nm.

  In the retardation plate according to the present invention, the order parameter ratio of the dichroic dye is preferably 0.7 to 1.2.

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

  According to the present invention, a display device including the retardation plate is provided.

  In the display device of the present invention, it is preferable that the maximum absorption wavelength of the dichroic dye contained in the retardation plate is different from the maximum wavelength of the emission spectrum of the display device.

  According to the present invention, it is possible to realize a retardation plate having a “negative dispersion” characteristic close to an ideal, in which a decrease in transmittance is minimized. Such a retardation plate functions as a retardation plate that converts circularly polarized light into linearly polarized light and linearly polarized light into circularly polarized light over a wide wavelength region in the front and oblique directions. For this reason, if the retardation plate is used for 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 for an organic EL display device, it is high in specular reflection at a wide viewing angle. The prevention performance is greatly improved.

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 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. In the reference example 3, it is a figure which shows the comparison with the wavelength dispersion of birefringence (DELTA) n before and after adding a dichroic dye to a liquid-crystal composition. It is a measurement result of the apparent retardation measured by inclining the optical film produced in Example 1 along the orientation direction of a liquid crystal. It is a figure which shows the layer structure of a laminated polarizing plate provided with the optical film produced in Examples 1-3 and Comparative Examples 1-3.

<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. Comprises a liquid crystal film comprising a polymerizable liquid crystal composition containing a liquid crystal compound and a dichroic dye, and the liquid crystal compound is nematic hybrid aligned in the liquid crystal film. Here, the nematic hybrid alignment is an alignment in which the directors of the liquid crystal compound are aligned at different angles when viewed from the film thickness direction.

  The refractive index wavelength dispersion characteristic of the liquid crystal compound 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 a region away from the intrinsic absorption wavelength (regions a1, a2, and a3 in FIG. 2), the refractive index n of the liquid crystal compound decreases monotonically as the wavelength increases. Such dispersion is called “normal dispersion”, and k = 0. On the other hand, the refractive index n in the wavelength region including intrinsic absorption (regions b1, b2, and b3 in FIG. 2) 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 extraordinary ray refractive index ne and the ordinary ray refractive index no both have “positive dispersion” characteristics in this region. Therefore, the prior art proposed as a method for obtaining “negative dispersion” characteristics comprises a mixture of an organic polymer having “positive birefringence” and a liquid crystal compound having “negative birefringence”.
In contrast, in the present invention, by adding a dichroic dye having absorption in the visible light region to the liquid crystal composition having “positive dispersion” characteristics, an extraordinary ray is emitted in a certain wavelength region in the visible light region. The refractive index ne exhibits a “negative dispersion” characteristic, and as a result, the birefringence Δn has a “negative dispersion” characteristic that is closer to the ideal.

In the retardation plate of the present invention, 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.
In the case of a liquid crystal film comprising a liquid crystal composition comprising a compound having two or more kinds of mesogenic groups and a rod-like liquid crystal compound exemplified in Patent Document 3, the “positive birefringence” and “negative” shown in FIG. A phase difference plate having "dispersion" characteristics is obtained. However, generally, as shown in FIG. 1, the long wavelength side deviates from the ideal straight line due to the difference in slope between the curve on the short wavelength side and the curve on the long wavelength side from the center wavelength of visible light of 550 nm. There is a tendency. Therefore, in order to approximate the ideal chromatic dispersion curve in a wide band of 400 to 700 nm, which is the visible light region, the curve on the long wavelength side is maintained by another method while maintaining the short wavelength side curve close to the ideal straight line. It is necessary to try to approximate the ideal straight line. In view of the above situation, the present inventors have focused on “negative dispersion” characteristics resulting from an anomalous dispersion region of a liquid crystal compound.

  FIG. 3 shows an enlarged view of the curve of “abnormal dispersion region” 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. 3 as λmax, λ +, and λ−. That is, there is a “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 thin lines in FIG. 4 (solid line is extraordinary ray refractive index ne, dotted line is ordinary ray refractive index no), generally, in the case of a liquid crystal compound having anisotropy, the type of dipole differs depending on the axial direction. The “positive dispersion” curve is different from no. By adding a dichroic dye having a maximum absorption wavelength at 580 nm as shown in FIG. 5 to this liquid crystal composition, ne has a “negative dispersion” characteristic in a wavelength region of 550 to 650 nm. Is obtained. The dichroic dye used here preferably exhibits high dichroism. High dichroism means that the difference between the absorption characteristics of ne and no is large. FIG. 6 shows the birefringence wavelength dispersion characteristics of a phase difference plate made of a liquid crystal compound before and after adding a dichroic dye. By adding a dichroic dye, a retardation plate having “negative dispersion” in which the birefringence is closer to the ideal is obtained in the wavelength region of 550 to 650 nm.

  The retardation plate of the present invention has a “negative dispersion” characteristic in which ne becomes larger as the measurement wavelength is longer in at least a part of the wavelength region of the visible light region, and accordingly, birefringence Δn is larger 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 ne exhibits “negative dispersion” characteristics, a region including a visible light center wavelength of around 550 nm is preferable. This is because the vicinity of 555 nm is maximized when the sensitivity of brightness perceived by the human eye for each wavelength is bright, and the vicinity of 507 nm is maximized when the sensitivity is dark.

The retardation plate of the present invention is a retardation plate characterized in that the birefringence Δn has a “negative dispersion” characteristic that becomes larger as the measurement wavelength is longer in the visible light region. More specifically, when retardation of the retardation plate at 500 nm, 550 nm, and 600 nm is Δn · d (500), Δn · d (550), and Δn · d (600), the following formula (3), ( It is preferable to satisfy 4), and it is more preferable to satisfy the following formulas (3-1) and (4-1). Here, the retardation is a product (Δn · d) of birefringence Δn and the thickness d of the retardation plate.
1.00> Δn · d (500) / Δn · d (550)> 0.80 (3)
1.15> Δn · d (600) / Δn · d (550)> 1.00 (4)
0.98> Δn · d (500) / Δn · d (550)> 0.90 (3-1)
1.10> Δn · d (600) / Δn · d (550)> 1.02 (4-1)
When the liquid crystal film has the above retardation characteristics, for example, when it is used as a ¼ wavelength plate, when the linearly polarized light having a wavelength of 400 to 700 nm is incident on the film, the circularly polarized light is good in a wide wavelength region. Can be obtained.

In the present invention, retardation of a retardation plate composed of a liquid crystal film containing a dichroic dye is Δna · da at a predetermined wavelength in the normal direction, 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)

<Liquid crystal film>
The liquid crystal film includes a polymerizable liquid crystal composition and a dichroic dye, and the liquid crystal compound included in the polymerizable liquid crystal composition has an alignment structure in which nematic hybrid alignment is performed. A liquid crystal film is a film in which a nematic hybrid alignment of a liquid crystal compound is fixed. The orientation of the liquid crystal film can be measured by measuring the retardation (Δn · d) of the film. In a state where the liquid crystal is aligned, Δn · d at a measurement wavelength of 550 nm is 20 nm or more.

  FIG. 7 shows a cross-sectional structure of a liquid crystal film comprising the liquid crystal compound with nematic hybrid alignment according to the present invention. Further, FIG. 8 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. In a liquid crystal film comprising a 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. Therefore, the retardation plate of the present invention has no optical axis in the entire film. Note that the tilt direction (axis) of the liquid crystal film means that 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 absolute value of the angle formed by the director of the liquid crystal compound in the vicinity of one film interface of the liquid crystal film is preferably 20 degrees to 90 degrees, more preferably Is 30 to 70 degrees, and the absolute value of the angle with the director near the film interface opposite to the film surface is preferably 0 to 50 degrees, more preferably 0 to 30 degrees. The absolute value of the average tilt angle in the nematic hybrid alignment structure is preferably 5 degrees to 40 degrees, more preferably 10 degrees to 35 degrees, and most preferably 15 degrees to 30 degrees. If the average tilt angle is within the above numerical range, the reflection viewing angle characteristics can be improved when the display device is provided in a liquid crystal display device or an organic EL display device in combination with a polarizer. Here, the average tilt angle is an average value of angles formed by the director of the liquid crystal compound 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 an optical anisotropic axis is twisted from one surface to the other surface of a director of the liquid crystal compound. 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 a liquid crystal cell, STN (super twisted nematic) liquid crystal cell, etc., it has retardation and twist angle when viewed from the normal direction of the film. 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 compound is twisted in the in-plane direction from the one surface to the other while the optical anisotropic axis is twisted. A film inclined at different angles. The absolute value of the twist angle in the alignment structure is preferably 0 ° to 70 °, more preferably 0 ° to 60 °, and most preferably 0 ° to 59 °. If the twist angle is within the above numerical range, display characteristics such as contrast and antireflection performance when viewed from the front can be improved when the display device is provided in combination with a polarizer. Here, although there are two types of twist angles, the twist angle may be a right twist or a left twist.
Such retardation, twist angle, and tilt angle are devices capable of measuring birefringence (for example, trade name “Axoscan” manufactured by Axometrix, trade name “KOBRA-21ADH” manufactured by Oji Scientific Instruments), etc.) It can calculate from the value measured using.

<Dichroic dye>
In the present invention, the dichroic dye refers to a dye having a property that the absorbance in the major axis direction of the molecule is different from the absorbance in the minor axis direction. Moreover, the dichroic dye in which the order parameter (S) represented by the following formula (1) of the dichroic dye in the retardation plate is in the range of 1.0 ≧ S ≧ 0.5 is used.
S = (DR-1) / (DR + 2) (1)
(In the formula (1), DR represents the following formula (2):
(In formula (5), λ represents the wavelength (nm) of light in vacuum,
Ae (λ) represents a polarization absorption spectrum parallel to the slow axis in the retardation plate,
Ao (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the retardation plate,
Ae0 (λ) represents a polarization absorption spectrum parallel to the slow axis in the retardation plate excluding the dichroic dye,
Ao0 (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the retardation plate excluding the dichroic dye. )
The dichroic ratio of the dichroic dye represented by ).
“Order parameter (S)” is an index representing the degree of orientation of the dichroic dye in the retardation plate, and is defined in the range of 1.0 ≧ S ≧ −0.5. In the retardation plate, the dichroic dye is perfectly oriented in one direction when S = 1, and is completely disordered when S = 0.

When a dichroic dye is added to a retardation plate having “positive dispersion” characteristics, the dichroic dye is oriented in the director direction of the polymerizable liquid crystal compound, but has a “negative dispersion” characteristic. In, mesogenic groups exist in a direction substantially perpendicular to the direction of the director of the liquid crystal compound. For this reason, compared with the case where a dichroic dye is added to a retardation plate having “positive dispersion” characteristics, the orientation of the dichroic dye is lowered, and as a result, the dichroic ratio tends to be lowered. .
In the present invention, when a dichroic dye having an order parameter (S) in the range of 1.0 ≧ S ≧ 0.5 is used, it is added to a retardation plate having “negative dispersion” characteristics. Even so, a high dichroic ratio can be maintained.

  The dichroic ratio of the dichroic dye is defined by the ratio of the absorbance at the maximum absorption wavelength in the major axis direction to the absorbance in the minor axis direction of the dichroic dye. The dichroic ratio can be determined by measuring the absorbance in the orientation direction of the dichroic dye and the absorbance in the direction perpendicular to the orientation direction. In the present invention, the dichroic ratio of the dichroic dye added to the retardation plate having “negative dispersion” characteristics is preferably 2 to 50, more preferably 5 to 30.

  There are no particular limitations on such dichroic dyes. Dye, 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, Examples thereof include stilbene dyes and indigo dyes. Among them, the dichroic dye is preferably an anthraquinone dye or an azo dye. Examples of the azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and stilbene azo dyes, and preferred examples include bisazo dyes, trisazo dyes, and derivatives of these series of dyes. Any dye that satisfies the above conditions can be used in the present invention. An example of a dye that can be used in the present invention is represented by the dye number described in the dye handbook (Nobu Okawara, Shinjiro Kitao, Tsuneaki Hirashima, Ken Matsuoka, Kodansha Scientific Co., Ltd., 1986, 1st edition). It is shown in 1.

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

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

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

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

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

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

  The dichroic dye preferably has a polymerizable group. For example, the polymerizable group is preferably an acryl group, a methacryl group, a vinyl group, a vinyloxy group, an epoxy group, or an oxetanyl group. In view of the above, an acrylic group, an epoxy group, and an oxetanyl group are particularly preferable. Since the dichroic dye has a polymerizable group, it is polymerized with the polymerizable liquid crystal composition and aligned on the alignment substrate in substantially the same direction as the alignment direction of the polymerizable liquid crystal composition. It is possible to reduce the “negative dispersion” characteristic below, and to prevent fluctuations in the absorbance and dichroic ratio of the dichroic dye, so that a retardation plate excellent in optical reliability can be obtained. Further, the dichroic dye may have liquid crystallinity, and those having a nematic phase and a smectic phase are particularly preferable.

Specific examples of the polymerizable dichroic dye having a polymerizable group include the following compounds.

As the anthraquinone dye, a compound represented by the formula (1-59) is preferable.
(In the formula, R ^{1 to} R ⁸ each independently represent a hydrogen atom, —R _x , —NH ₂ , —NHR _x , —NR _{x 2} , —SR _x, or a halogen atom. Rx represents 1 carbon atom. Represents an alkyl group of ˜4 or an aryl group of 6 to 12 carbon atoms.)

Moreover, as an oxazone pigment | dye, the compound represented by Formula (1-60) is preferable.
(In the formula, R ^{9 to} R ¹⁵ each independently represent a hydrogen atom, —R _x , —NH ₂ , —NHR _x , —NR _{x 2} , —SR _x, or a halogen atom. R _x represents the number of carbon atoms. Represents an alkyl group having 1 to 4 or an aryl group having 6 to 12 carbon atoms.)

Moreover, as an acridine pigment | dye, the compound represented by Formula (1-61) is preferable.
(In the formula, R ^{16 to} R ²³ each independently represent a hydrogen atom, —R _x , —NH ₂ , —NHR _x , —NR _{x 2} , —SR _x, or a halogen atom. R _x represents the number of carbon atoms. Represents an alkyl group having 1 to 4 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 R _x is a methyl group, an ethyl group, a propyl group, a butyl group, Examples thereof include a pentyl group and a hexyl group, and examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a toluyl group, a xylyl group, and a naphthyl group.

Moreover, as a cyanine dye, the compound represented by Formula (1-62) and the compound represented by Formula (1-63) are preferable.
(In the formula, D ¹ and D ² each independently represent a group represented by any of the following formulas (1-62a) to (1-62d), and n5 represents an integer of 1 to 3). .)
(In Formula (1-63), D ³ and D ⁴ each independently represent a group represented by any of the following Formulas (1-63a) to (1-63h); Represents an integer of 3.)

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

  The dichroic dye is preferably a rod-like molecule. Furthermore, the molecular length in the major axis direction is preferably 2 to 10 nm, more preferably 2.3 to 8 nm, and even more preferably 2.5 to 6 nm. Here, the “long-axis molecular length” means the longest distance among the distances between atoms excluding non-cyclic functional groups and hydrogen atoms present at both ends of the dichroic dye. And a functional group in which a linear aliphatic hydrocarbon group, a vinyl group, a carbonyl group, an alcohol group, an alkoxy group, an ether group, and the functional group are bonded via a non-cyclic aliphatic hydrocarbon group, and The functional group includes a hydrogen atom substituted with a halogen atom, and does not include an aromatic ring group, an unsaturated heterocyclic group or an aliphatic ring group. Density functional method (DFT method) using the quantum chemistry calculation package (ORCA Ver3.0.1) for the initial configuration of the conformation that maximizes the molecular length (for example, trans configuration for molecules having an azo group) The molecular length can be calculated by performing the most stable structure calculation. Further, PBE0 can be used as the functional, and Def2-SVP can be used as the basis. By using a dichroic dye having a molecular length of 2 nm to 10 nm, the order parameter (S) can be brought close to 1.0 even when added to a retardation plate having “negative dispersion” characteristics. .

  Order parameter ratio of dichroic dye (order parameter (S) when dichroic dye is added to a retardation plate having “negative dispersion” characteristics) / two-color retardation film having “positive dispersion” characteristics The order parameter (S) in the case of adding a functional dye is preferably 0.7 to 1.2, more preferably 0.8 to 1.1, and 0.9 to 1.1. More preferably it is.

  The dichroic dye preferably has a maximum absorption wavelength (λmax) in the range of 380 to 780 nm, more preferably 400 to 750 nm, particularly preferably 450 to 700 nm, and most preferably 540 to 620 nm. When the retardation plate of the present invention is applied to a display device such as an image display device, a maximum absorption wavelength different from the maximum absorption wavelength of the emission spectrum of the image display device is taken into consideration in consideration of the emission spectrum of the light source of the display device. Most preferably, the maximum absorption wavelength of the dichroic dye is different from the maximum wavelength of the emission spectrum of the display device.

  The light emission spectra of the red, blue, and green light emitting elements of the organic EL image display device have a maximum value at a wavelength of about 460 nm for blue light, a wavelength of about 530 nm for green light, and a wavelength of about 630 nm for red light. When the retardation plate of the present invention is applied to an organic EL image display device, light absorption by a dichroic dye is inevitable, but an emission spectrum of three colors is used to minimize the decrease in transmittance due to this absorption. It is preferable to select a dichroic dye having a maximum absorption wavelength different from the maximum wavelength. For example, it is preferable to apply a dichroic dye having a maximum absorption wavelength around 580 nm. The same applies to other image display devices. In a liquid crystal image display device using an LED as a light source, a decrease in transmittance is suppressed by using a dichroic dye having a maximum absorption wavelength different from the maximum wavelength of the LED. be able to. The difference between the maximum absorption wavelength of the dichroic dye and the maximum wavelength of the emission spectrum of the image display device is 5 nm or more, preferably 10 nm or more, and more preferably 20 nm or more. By setting the difference between the maximum absorption wavelength of the dichroic dye and the maximum wavelength of the emission spectrum of the image display device to be 5 nm or more, a decrease in transmittance can be suppressed.

  The content of the dichroic dye in the phase difference plate can be adjusted as appropriate according to the type of the dichroic dye. In the present invention, the order parameter (S) is 1.0 ≧ S ≧ 0.5. Therefore, a high reverse dispersibility improvement effect can be maintained while suppressing the content of the dichroic dye. Specifically, it is 0.03 to 0.8 part by weight and preferably 0.05 to 0.5 part by weight with respect to 100 parts by weight of the polymerizable liquid crystal composition. In the present invention, since the content of the dichroic dye can be suppressed to a small amount, a decrease in the transmittance of the retardation plate can be suppressed. In addition, content of dichroic pigment | dye here means the total amount, when two or more types of dichroic pigment | dye are included.

<Polymerizable liquid crystal composition>
The polymerizable liquid crystal composition is not particularly limited as long as it can fix the nematic hybrid alignment state of the liquid crystal compound by polymerization. The polymerizable liquid crystal composition in the present invention is
(1) One or two or more polymerizable liquid crystal compounds,
(2) a liquid crystal compound having no polymerizable group and a polymerizable non-liquid crystal compound;
Any of (3) a polymerizable liquid crystal compound and a polymerizable non-liquid crystal compound, and (4) a polymerizable liquid crystal compound and a liquid crystal compound having no polymerizable group may be used.

  In the present invention, known polymerizable liquid crystal compounds can be appropriately used. As such a polymerizable liquid crystal compound, it is preferable to use a polymerizable liquid crystal compound capable of nematic hybrid alignment on an alignment substrate and fixing the alignment state. Furthermore, as such a polymerizable liquid crystal compound, for example, a low molecular polymerizable liquid crystal compound, a high molecular polymerizable liquid crystal compound, and a mixture thereof can be appropriately used.

  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.

  In the present invention, the retardation Δn · d preferably satisfies the above mathematical expressions (3) and (4). As the compound satisfying the above formula (3), a compound in which the polymerizable liquid crystal compound has two or more kinds of mesogenic groups is known, and at least one of the mesogenic groups is a slow phase of parallel (homogeneous) alignment of the liquid crystal layer. By orienting in a direction substantially orthogonal to the axis, the longer the wavelength, the greater the phase difference. Here, the mesogen of the mesogen group is also referred to as 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) It is almost synonymous with liquid crystal molecular structure.

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

  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.

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.

  As the liquid crystal compound having two or more kinds of mesogenic groups, a commercially available product may be used and 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. Such polymerizable liquid crystal compounds may be used alone or as 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.

  The polymerizable liquid crystal composition may use a mixture of a liquid crystal compound having a polymerizable group and a polymerizable compound that does not exhibit liquid crystallinity. Such a polymerizable compound not exhibiting liquid crystallinity is particularly limited as long as it is compatible with a liquid crystal compound having a polymerizable group and does not cause alignment inhibition when the liquid crystal compound is aligned. Not. Examples of such a polymerizable compound that does not exhibit liquid crystallinity include compounds having a polymerizable functional group such as an ethylenically unsaturated group (for example, a vinyl group, a vinyloxy group, or a (meth) acryloyl group). The addition amount of the polymerizable compound not exhibiting liquid crystallinity should be 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. Preferably, the content is 1 to 30% by weight.

<Polymerization initiator>
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, and the polymerizable liquid crystal compound in the composition Depending on the type, a material capable of initiating polymerization of the polymerizable liquid crystal compound more efficiently may be appropriately selected and used. 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) A photoinitiator is more preferable.

  As the 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”) Alternatively, a photopolymerization initiator (trade name “UVI6974”) manufactured by Union Carbide may be used as appropriate. Such photopolymerization initiators include those that generate free radicals and those that generate ions upon irradiation with light or an electron beam, and the type of polymerizable liquid crystal compound in the polymerizable liquid crystal composition. Or 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). What is necessary is just to select suitably and use suitably from a Carbide company make, brand name: UVI6974).

  Moreover, as content of the polymerization initiator which concerns on this invention, it is preferable that it is 1-10 weight part with respect to 100 weight part of mixture of a polymeric liquid crystal composition and a dichroic dye, and 3-5 weight part is preferable. More preferably. If content of such a polymerization initiator is in the said numerical range, the sclerosis | hardenability of the obtained phase difference plate is enough, and it can suppress producing a defect in the orientation of a liquid crystal compound.

<Method for producing retardation plate>
A method for producing a retardation film comprising the liquid crystal film of the present invention will be described.
The production method of the retardation plate is not particularly limited. For example, (1) a polymerizable liquid crystal composition, a dichroic dye, and various solvents, additives, and polymerization that are added as necessary. A solution adjusting step for preparing a composition solution containing an initiator and the like; (2) a coating step for forming a coating film by coating the composition solution on an alignment substrate; and (3) a liquid crystal by heat-treating the coating film. It can be manufactured through an orientation step for orientation, (4) an orientation immobilization step for immobilizing nematic hybrid orientation by light irradiation and / or heat treatment (polymerization / crosslinking) or the like.

  In this specification, the state “fixed in the state of nematic hybrid alignment” means that the nematic hybrid alignment is confirmed in the liquid crystal film obtained by fixing the alignment of the liquid crystal compound by the polymerization reaction of the polymerizable liquid crystal composition. A state of a component derived from a polymerizable liquid crystal compound or the like (including 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 alignment state.

(Solution adjustment process)
The solvent used for preparing the solution is not particularly limited as long as it can dissolve the polymerizable liquid crystal composition and the dichroic dye and can be distilled off under appropriate conditions. For example, from the viewpoint of drying speed suitable for applying a solution so as to obtain a uniform film thickness, ease of handling (harmful to the environment), and solubility in polymerizable liquid crystal compositions and dichroic dyes, propylene Glycol 1-monomethyl ether 2-acetate, 2-methoxyethyl acetate, toluene, xylen, methoxybenzene, 1,2-methoxybenzene, cyclohexanone, cyclopentanone, methyl cellosolve, ethyl cellosolve, butyl cellosolve, γ-butyrolactone are preferred, propylene Glycol 1-monomethyl ether 2-acetate and γ-butyrolactone are more preferred. In addition, you may utilize 1 type as such a solvent individually or in combination of 2 or more types. In addition, depending on the type of the substrate, corrosion may occur depending on the type of the solvent. Therefore, it is preferable to select and use a suitable solvent according to the type of the substrate.

  Further, 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 composition and the dichroic dye is secured, so that the precipitation of the liquid crystal compound during storage can be suppressed, It is possible to prevent the wettability from being lowered due to an increase in the viscosity of the mixture, and it is possible to satisfactorily perform coating during the production of the retardation plate. Further, when the content of the solvent is 95% by weight or less, the removal (drying) of the solvent is completed in a short time, so that the productivity can be prevented from decreasing. Furthermore, since the fluidity of the surface is suppressed when a solution containing the mixture is coated on the alignment substrate, a retardation plate having a uniform quality can be manufactured. 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.

  As the alignment substrate, one having a smooth plane is preferable, and a film or sheet made of an organic polymer material, a glass plate, a metal plate, or the like can be used. Examples of organic polymer materials include polyvinyl alcohol, polyimide, polyamide, polyamideimide, polyphenylene sulfide, polyether sulfone, polyphenylene oxide, polyether ketone, polyether ether ketone, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) And polysulfone, cyclopolyolefin having a cyclic or norbornene structure, diacetyl cellulose, triacetyl cellulose (TAC), cellulose acetate, cellulose propionate, cellulose butyrate, epoxy resin, phenol resin and the like. Such an alignment substrate is not particularly limited, but an optical function such as a retardation function is used depending on its use, such as using a laminate of the liquid crystal film and the alignment substrate as it is as an optical film. It is good also as what has. Further, such an oriented substrate may be a uniaxially stretched film or a biaxially stretched film.

(Coating process)
The application method is not particularly limited as long as the uniformity of the coating film is ensured, and a known method can be adopted. Examples thereof include spin coating, die coating, curtain coating, dip coating, and roll coating. Such a coating film varies depending on the content of the solvent in the polymerizable liquid crystal composition and the dichroic dye mixture of the present invention, and cannot be generally stated, 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, if it is 20 micrometers or less, since the density | concentration of the solid content in a liquid-crystal composition for setting it as a desired optical characteristic will become thin, the drying time after application | coating can be shortened.

(Orientation process)
After applying the solution containing the polymerizable liquid crystal composition, heating is preferably performed for the purpose of removing the solvent and aligning the liquid crystal compound. The heating temperature is preferably 15 to 110 ° C, and more preferably 20 to 80 ° C. If temperature is 15 degreeC or more, a cooling installation is not required and a liquid crystal compound can be aligned efficiently. Moreover, if it is 110 degrees C or less, it can suppress that an orientation substrate is distorted with a heat | fever and an optical characteristic etc. change.

Moreover, it is preferable that it is 600-1400 hPa in the pressure in this orientation process, 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. The heating time is preferably 10 seconds to 60 minutes, more preferably 1 minute to 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. Examples of the apparatus that can be used for heating include a heater (furnace) and a hot air blowing apparatus.

(Orientation fixing process)
As a method for fixing the alignment state of the liquid crystal compound by polymerizing the polymerizable liquid crystal composition, for example, depending on the type of the polymerization initiator, the polymerizable group is reacted by light irradiation and / or heat treatment. You may employ | adopt the method of fixing orientation.

When the polymerization initiator is such that it exhibits a function as an initiator by light irradiation (for example, in the case of a so-called photocation generator), the alignment state of the nematic hybrid alignment is fixed by light irradiation. It is preferable. The light irradiation method is not particularly limited. For example, a light source having a spectrum in the absorption wavelength region of the polymerization initiator used (for example, a metal halide lamp, an intermediate pressure or a high pressure mercury lamp having an illuminance of 10 mW / cm ² or more. (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, from the viewpoint of fixing the coating film while maintaining the orientation state more efficiently, a suitable photosensitizer and two or more polymerization initiators having different absorption wavelengths are mixed and used. May be. 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. Note that a cold mirror or other cooling device may be provided between the alignment substrate and the light source (such as an ultraviolet lamp) so that the surface temperature of the coating film can maintain the liquid crystal temperature range during light irradiation.

  The conditions of the atmosphere at the time of light irradiation are not particularly limited, and may be an air atmosphere or a nitrogen atmosphere in which oxygen is blocked 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 has a function as an initiator by heat (for example, in the case of a so-called thermal cation generator), the alignment is fixed in the alignment state of the nematic hybrid alignment by heat treatment. It is preferable to do. The conditions for such heat treatment are not particularly limited, and the temperature condition may be selected so that the orientation state is sufficiently maintained according to the type of the polymerization initiator, and known conditions are appropriately adopted. Can do.
When the alignment substrate has low heat resistance, a 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.

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

  As a method for confirming the nematic hybrid alignment, a known method can be adopted as appropriate, and is not particularly limited, but a pair of orthogonal polarizing plates (the deflection direction of one deflection plate and the deflection direction of the other deflection plate are different). A method of confirming the transmitted light of a sample in which a liquid crystal film (which may be in a state of a laminate with a substrate) is placed between a pair of orthogonal polarizing plates) or a method of confirming using a polarizing microscope It may be adopted. When checking with the naked eye, place the sample on the backlight when viewed from the front, adjust the sample angle so that the transmitted light intensity from the backlight is the weakest, and tilt the slow axis as the axis. It is possible to confirm the presence or absence of nematic hybrid alignment by confirming that the transmitted light intensity becomes strong when observed from above and that the transmitted light intensity remains weak when observed obliquely with the fast axis as the axis. it can. In addition, since the nematic hybrid alignment liquid crystal film has different retardation characteristics depending on the incident angle of light, the retardation in the vertical direction with respect to the surface of the liquid crystal film and the incident angle of light from the vertical direction to a specific angle are set. Using a birefringence measuring apparatus capable of measuring the retardation when tilted (for example, trade name “Axoscan” manufactured by Axo-metrix, trade name “KOBRA-21ADH” manufactured by Oji Scientific Instruments, etc.) The phase difference is measured while appropriately changing the angle from a viewing angle of 0 degrees (perpendicular to the liquid crystal film) to a direction in which the viewing angle becomes larger, and the retardation of the sample is obtained for each of the viewing angles. Retardation is confirmed in the direction perpendicular to the film surface, and the viewing angle is further increased. Deshon is, the viewing angle - the value of the direction and the + direction to exhibit asymmetry, by checking the may be adopted a method of confirming the presence or absence of a nematic hybrid orientation.

  The thickness of the liquid crystal film is preferably 0.1 to 10 [mu] m, more preferably 0.2 to 5 [mu] m, although it varies depending on the application and required characteristics. If the thickness of the liquid crystal film is 0.1 μm or more, a desired phase difference can be expressed, and if it is 10 μm or less, a decrease in the orientation of the liquid crystal can be suppressed or a decrease in the transmittance due to the dye can be suppressed. .

  The birefringence Δn of such a liquid crystal film is preferably 0.005 to 0.5, and more preferably 0.01 to 0.3, although it varies depending on the application and required characteristics. If birefringence (DELTA) n is said range, when it is set as desired retardation, 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 according to the present invention comprises a retardation plate comprising a liquid crystal film and a polarizer. 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.

  A laminated polarizing plate can be prepared by laminating a retardation plate and a polarizer to each other via an adhesive layer. However, when the retardation plate is made of a liquid crystal film as in the present invention, it is polymerizable. It can be prepared by applying a mixture of a liquid crystal composition and a dichroic dye directly or through an alignment film on a polarizer 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 nematic hybrid alignment is fixed, the upper and lower sides of the film are not optically equivalent. Therefore, the display performance varies depending on which film surface of the liquid crystal film is on the polarizing plate side and in combination with optical parameters such as a liquid crystal cell. Therefore, when the liquid crystal film of the present invention is used for a laminated polarizing plate, it is desirable to determine the arrangement conditions in consideration of required optical characteristics, display characteristics, and the like.

<Display device>
The display apparatus of this invention is equipped with the phase difference plate which consists of said liquid-crystal film. 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. As the display device of the present invention, the type of the image display device is not particularly limited, and a known display device such as a liquid crystal display device, an organic EL display device, a plasma display, or the like can be appropriately used. 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 of the present invention. 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.

  In the liquid crystal display device of the present invention, since the retardation plate has a desired birefringence wavelength dispersion characteristic, for example, the viewing angle of the liquid crystal display apparatus is sufficiently widened or the luminance is sufficiently improved according to the characteristic. This makes it possible to sufficiently improve the viewing angle and the image quality.

An organic EL display device including the retardation plate of the present invention will be described.
Generally, in an organic EL display device, an organic light emitting layer is formed by sequentially laminating a transparent electrode, an organic light emitting layer, and a metal electrode on a transparent substrate. 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 EL 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. In addition, by providing a retardation plate between the transparent electrode and the polarizing plate, it is possible to suppress the reflected light from the metal electrode. 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 composed of a quarter-wave plate and a linear polarizer and a retardation plate are combined. Can do.

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. The angle formed between the absorption axis of the polarizing plate and the slow axis of the quarter-wave plate is preferably 40 to 50 degrees, more preferably 42 degrees when the retardation plate of the present invention is nematic hybrid alignment. It is -48 degree | times, More preferably, it is the range of about 45 degree | times. 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 The alignment state of the liquid crystal was observed using a polarizing microscope (Olympus Optical Co., Ltd., model number: BH2).
(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 It measured using the automatic birefringence meter (Axometrics company make, brand name: Axoscan).
(4) Polarization absorption spectrum of dichroic dye Measured using a spectrophotometer (trade name: V-570, manufactured by JASCO Corporation).

(Reference Example 1)
(Preparation of alignment substrate)
The alignment substrate was produced as follows. A polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., trade name: Cosmo Shine A4100) is cut into 15 cm square, and 5 weight of alkyl-modified polyvinyl alcohol (PVA) (manufactured by Kuraray Co., Ltd., trade name: MP-203). % Solution (solvent is a mixed solvent of water and isopropyl alcohol at 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 the rubbing cloth / moving speed of the alignment substrate) was 4.

(Reference Example 2)
(Preparation of mixed solution of polymerizable liquid crystal compound (A) and dichroic dye (D1))
A polymerizable liquid crystal compound (A) (manufactured by BASF, trade name: Paliocolor LC242) is mixed with a dichroic dye (D1) (maximum absorption wavelength 560 nm) represented by the following formula and a polymerizable liquid crystal compound (A). 1 part by weight with respect to 100 parts by weight of the total amount of the functional dye (D1), and 4.0 wt. Of a polymerization initiator (manufactured by BASF, trade name: LUCIRIN TPO, solid at room temperature (25 ° C.)) A liquid crystal composition (AD1) formed by mixing a polymerizable liquid crystal compound (A), a dichroic dye (D1), and a polymerization initiator was obtained.

Next, the liquid crystal composition (AD1) was dissolved in chlorobenzene, and the insoluble matter was filtered with a polytetrafluoroethylene (PTFE) filter (Advantech Toyo Co., Ltd., trade name: 25JP050AN) having a pore size of 0.45 μm. A liquid crystal composition (AD1) solution was obtained. In the production of such a liquid crystal composition (AD1) solution, the content of the solvent in the liquid crystal composition (AD1) solution is 80% by weight, and the polymerizable liquid crystal compound (A) and the dichroic dye ( The solvent was used so that the total content of D1) and the polymerization initiator was 20% by weight.

  The molecular length excluding the terminal alkyl chain of the dichroic dye (D1) was evaluated from the three-dimensional structure of the molecule obtained by quantum chemical calculation. Density functional method (DFT method) using the quantum chemistry calculation package (ORCA Ver 3.0.1) in the initial configuration with a conformation that maximizes the molecular length of the azo group in the trans form and other sites The most stable structure was implemented. The functional was PBE0, and the basis was Def2-SVP. The molecular length (excluding the terminal alkyl chain) of the dichroic dye (D1) measured by the above method was 2.15 nm.

(Production of liquid crystal film)
The liquid crystal composition (AD1) solution obtained as described above is applied to the alignment substrate obtained in Reference Example 1 by spin coating 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 allowed to stand for 4 minutes under the conditions of pressure: 1013 hPa and temperature: 80 ° C. to align the liquid crystal. In addition, the solvent was removed from the entire surface of the coating film after 4 minutes had passed since the coating on the alignment substrate was completed.
Next, using a high-pressure mercury lamp with an illuminance of 15 mW / cm ² , the polymerizable liquid crystal compound (A) is irradiated by irradiating ultraviolet light so that the integrated irradiation amount is 200 mJ / cm ² (light quantity with a wavelength of 365 nm). The liquid crystal film laminated | stacked on the orientation board | substrate was obtained by superposing | polymerizing and fixing the orientation.

The PET film used as the alignment substrate has a large birefringence and is not preferable as an optical film. Therefore, an adhesive is applied on the liquid crystal film on the PET film so as to have a thickness of 5 μm, a TAC film (manufactured by Fuji Film Co., Ltd., trade name: T40UZ) is laminated, and ultraviolet rays are irradiated from the TAC film side. After the adhesive was cured, the PET film was peeled off.
When the obtained optical film (A) (liquid crystal film / adhesive layer / TAC film) was observed under a polarizing microscope, it was found that there was no disclination and uniform orientation of monodomains.

  The polarization absorption spectrum of the optical film (A) was measured using a spectrophotometer and an adapter capable of inserting a polarizing prism in the optical path. Ae (λ) is the polarization absorption spectrum measured with the easy transmission axis of the polarizing prism inserted in the optical path parallel to the slow axis of the liquid crystal film, and the polarization absorption spectrum measured with the easy transmission axis and the slow axis perpendicular. Ao (λ) was set.

  Further, an optical film (B) was prepared in the same manner as above except that the dichroic dye (D1) was not added to the liquid crystal composition (AD1), and the polarization absorption spectrum parallel to the slow axis was Ae0 (λ ), Ao0 (λ) was measured for the polarization absorption spectrum perpendicular to the slow axis.

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

(Reference Example 3)
(Preparation of mixed solution of polymerizable liquid crystal composition (B) and dichroic dye (D1))
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.

  17.6 parts by weight of the rod-like liquid crystal compound (21) and 2 parts by weight of the compound (22) having two or more kinds of mesogenic groups were mixed to obtain a polymerizable liquid crystal composition (B). Next, 1.0 part by weight of the dichroic dye (D1) was added to 100 parts by weight of the polymerizable liquid crystal composition (B). Furthermore, 1.0 part by weight of a polymerization initiator (manufactured by BASF, trade name: Irgacure 651) is added to 100 parts by weight of the total amount of the polymerizable liquid crystal composition (B) and the dichroic dye (D1). Thus, a polymerizable liquid crystal composition (B), a dichroic dye (D1), and a polymerization initiator were mixed to obtain a liquid crystal composition (BD1)).

  The liquid crystal composition (BD1) obtained as described above was dissolved in methyl ethyl ketone, and the insoluble matter was filtered with a PTFE filter having a pore diameter of 0.45 μm to obtain a liquid crystal composition (BD1) solution. In the production of such a liquid crystal composition (BD1) solution, the content of the solvent in the liquid crystal composition (BD1) solution is 80% by weight, and the polymerizable liquid crystal composition (B) and the dichroic dye ( The total amount of D1) and the polymerization initiator was set to 20% by weight.

(Production of liquid crystal film)
Except that the liquid crystal composition (BD1) was used in place of the liquid crystal composition (AD1), and that the alignment process was performed by holding at pressure: 1013 hPa, temperature: 72 ° C. for 2 minutes and then rapidly cooling to room temperature. In the same manner as in Reference Example 2, an optical film (C) (liquid crystal film / adhesive layer / TAC film) was obtained. When the obtained optical film (C) was observed under a polarizing microscope, it was found that there was no disclination and the monodomain was uniformly oriented.

  By measuring the wavelength dispersion characteristics of the optical film (C) (and the retardation (Δnd) in the in-plane direction of the TAC film alone using an automatic birefringence meter, and determining the difference between the two, the birefringence of the liquid crystal film The chromatic dispersion characteristics were calculated (FIG. 9): Δn · d (500) / Δn · d (550) = 0.898 and Δn · d (580) / Δn · d (550) = 1.049. In addition, Δn · d at 550 nm was 141.6 nm.

  Further, an optical film (D) was produced in the same manner as described above except that the dichroic dye (D1) was not added to the liquid crystal composition (BD1). The result of having measured the wavelength dispersion characteristic of this optical film (D) is shown in FIG. Δn · d (500) / Δn · d (550) = 0.981 and Δn · d (580) / Δn · d (550) = 1.09. In addition, Δn · d at 550 nm was 139.0 nm. The liquid crystal film comprising the polymerizable liquid crystal composition (B) was found to have “negative dispersion” characteristics at wavelengths from 400 nm to 600 nm even without the addition of the dichroic dye (D1). .

  In the obtained optical film (D), the liquid crystal film has a uniform tilt alignment and is not a nematic hybrid alignment film but a homogeneous alignment film by the method described in Examples of JP-A-11-194325. confirmed. As a result of analysis, the average tilt angle of the liquid crystal film was 0.4 degree, and the tilt angle at the TAC film side interface was 0.1 degree.

  When the dichroic ratio and order parameter (S) of the dichroic dye (D1) were evaluated using the optical film (C) and the optical film (D) in the same manner as in Reference Example 2, the dichroic ratio was 4. 3 and the order parameter was 0.52. The dichroic dye (D1) was found to have an order parameter ratio of 0.86 when compared to Reference Example 2 having a “positive dispersion” characteristic comprising the polymerizable liquid crystal compound (A). .

Example 1
(Production of liquid crystal film)
The addition amount of the dichroic dye (D1) was set to 0.065 parts by weight with respect to 100 parts by weight of the polymerizable liquid crystal composition (B), and the alignment step was started from pressure: 1013 hPa and temperature: 72 ° C. Optical film (1) (liquid crystal film / adhesive layer / TAC film) in the same manner as in Reference Example 3 except that the film was gradually cooled to 62 ° C. over 10 minutes and then rapidly cooled to room temperature. Got. When the obtained optical film (1) was observed under a polarizing microscope, it was found that there was no disclination and the monodomain was uniformly oriented.

The birefringence of the optical film (1) is measured by measuring the wavelength dispersion characteristics of the retardation (Δnd) in the in-plane direction of the optical film (1) and the TAC film using an automatic birefringence meter, and subtracting both. The wavelength dispersion characteristics of were measured. Δn · d at 550 nm is 140.9 nm, and Δn · d (500) / Δn · d (550) = 0.978 and Δn · d (580) / Δn · d (550) = 1.010. It was.
The retardation of the obtained optical film (1) when tilted in the rubbing direction (alignment direction of liquid crystal molecules) was measured using an automatic birefringence meter. 10) It was found that the film was tilted. The obtained liquid crystal film was confirmed to be a nematic hybrid alignment film rather than a uniform tilt alignment by the method described in Examples of JP-A-11-194325. As a result of analysis, the average tilt angle of the liquid crystal film was 24 degrees, and the tilt angle at the TAC film side interface was 45 degrees.

(Example 2)
As a dichroic dye, instead of the dichroic dye (D1), a dichroic dye (D2) (maximum absorption wavelength 570 nm) represented by the following formula is used with respect to 100 parts by weight of the polymerizable liquid crystal composition (B). An optical film (2) (liquid crystal film / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that 0.043 part by weight was added.

When the wavelength dispersion characteristic of the optical film (2) was measured, Δn · d at 550 nm was 140.5 nm, Δn · d (500) / Δn · d (550) = 0.980, Δn · d (580 ) / Δn · d (550) = 1.010. The average tilt angle of the liquid crystal film was 24 degrees, and the tilt angle at the interface on the TAC film side was 45 degrees.

(Evaluation of dichroic ratio of pigment)
A liquid crystal having a “positive dispersion” characteristic comprising the polymerizable liquid crystal compound (A) in the same manner as in Reference Example 2 except that the dichroic dye (D2) was used instead of the dichroic dye (D1). When the dichroic ratio and order parameter (S) of the dichroic dye (D2) in the film were evaluated, the dichroic ratio was 5.4 and the order parameter was 0.59.

  Except for using the dichroic dye (D2) instead of the dichroic dye (D1), the “negative dispersion” characteristic comprising the polymerizable liquid crystal composition (B) was obtained in the same manner as in Reference Example 3. When the dichroic ratio of the dichroic dye (D2) in the liquid crystal film was evaluated, the dichroic ratio was 4.4, and the order parameter was 0.53. When compared with the case where the same dichroic dye (D2) was added to the liquid crystal film containing the polymerizable liquid crystal compound (A), it was found that the order parameter ratio was 0.89. Further, the molecular length of the dichroic dye (D2) excluding the terminal alkyl chain was evaluated by the same method as in Reference Example 2, and it was 2.33 nm.

(Example 3)
Instead of the dichroic dye (D1), the dichroic dye (D3) (maximum absorption wavelength 550 nm) represented by the following formula was added to the polymerizable liquid crystal composition (B) by 100 parts by weight. An optical film (3) (liquid crystal film / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that 062 parts by weight were added.

When the wavelength dispersion characteristic of the optical film (3) was measured, Δn · d at 550 nm was 140.8 nm, Δn · d (500) / Δn · d (550) = 0.978, Δn · d (580 ) / Δn · d (550) = 1.003. The average tilt angle of the liquid crystal film was 24 degrees, and the tilt angle at the interface on the TAC film side was 45 degrees.

(Evaluation of dichroic ratio of pigment)
Except for using the dichroic dye (D3) in place of the dichroic dye (D1), it has “positive dispersion” characteristics comprising the polymerizable liquid crystal compound (A) in the same manner as in Reference Example 2. When the dichroic ratio and order parameter (S) of the dichroic dye (D3) in the liquid crystal film were evaluated, the dichroic ratio was 6.3 and the order parameter S was 0.64.

  “Positive dispersion” characteristics comprising the polymerizable liquid crystal composition (B) in the same manner as in Reference Example 3, except that the dichroic dye (D3) was used instead of the dichroic dye (D1). Evaluation of the dichroic ratio of the dichroic dye (D3) and the order parameter (S) in the liquid crystal film having a dichroic ratio of 6.5 and an order parameter of 0.65. As compared with the case where the same dichroic dye (D3) was added to the liquid crystal film containing the polymerizable liquid crystal compound (A), it was found that the order parameter ratio was 1.02. Further, the molecular length of the dichroic dye (D3) excluding the terminal alkyl chain was evaluated by the same method as in Reference Example 2, and it was 2.78 nm.

(Comparative Example 1)
Instead of the dichroic dye (D1), 0.081 parts by weight of the dichroic dye (D4) (maximum absorption wavelength 580 nm) represented by the following formula is used with respect to 100 parts by weight of the polymerizable liquid crystal composition (B). An optical film (4) (liquid crystal film / adhesive layer / TAC film) was obtained in the same manner as Example 1 except for the addition.

When the wavelength dispersion characteristic of the optical film (4) was measured, Δn · d at 550 nm was 140.7 nm, Δn · d (500) / Δn · d (550) = 0.799, Δn · d (580 ) / Δn · d (550) = 1.014. The average tilt angle of the liquid crystal film was 24 degrees, and the tilt angle at the interface on the TAC film side was 45 degrees.

(Evaluation of dichroic ratio of pigment)
Except for using the dichroic dye (D4) instead of the dichroic dye (D1), it has the “positive dispersion” characteristic comprising the polymerizable liquid crystal compound (A) in the same manner as in Reference Example 2. When the dichroic ratio and order parameter (S) of the dichroic dye (D4) in the liquid crystal film were evaluated, the dichroic ratio was 3.1 and the order parameter was 0.41.

  “Positive dispersion” characteristics comprising the polymerizable liquid crystal composition (B) in the same manner as in Reference Example 3 except that the dichroic dye (D4) was used instead of the dichroic dye (D1). Evaluation of the dichroic ratio of the dichroic dye (D4) and the order parameter (S) in the liquid crystal film having a dichroic ratio of 1.8 and an order parameter of 0.21. Compared to the case where the same dichroic dye (D4) was added to the liquid crystal film containing the polymerizable liquid crystal compound (A), the order parameter ratio was 0.52. Further, the molecular length of the dichroic dye (D4) excluding the terminal alkyl chain was evaluated by the same method as in Reference Example 2, and it was 1.31 nm. These results are summarized in Table 2.

(Comparative Example 2)
Instead of the dichroic dye (D1), the dichroic dye (D5) (maximum absorption wavelength 600 nm) represented by the following formula was added to 0.100 with respect to 100 parts by weight of the polymerizable liquid crystal composition (B). An optical film (5) (liquid crystal film / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except for adding parts by weight.

When the wavelength dispersion characteristic of the optical film (5) was measured, Δn · d at 550 nm was 140.5 nm, Δn · d (500) / Δn · d (550) = 0.980, Δn · d (580 ) / Δn · d (550) = 1.010. The average tilt angle of the liquid crystal film was 24 degrees, and the tilt angle at the interface on the TAC film side was 45 degrees.

(Evaluation of dichroic ratio of pigment)
Except for using the dichroic dye (D5) instead of the dichroic dye (D1), it has the “positive dispersion” characteristic comprising the polymerizable liquid crystal compound (A) in the same manner as in Reference Example 2. When the dichroic ratio and order parameter (S) of the dichroic dye (D5) in the liquid crystal film were evaluated, the dichroic ratio was 2.5 and the order parameter S was 0.34.

  Except that the dichroic dye (D5) was used instead of the dichroic dye (D1), the “positive dispersion” characteristic comprising the polymerizable liquid crystal composition (B) was obtained in the same manner as in Reference Example 3. When the dichroic ratio and order parameter (S) of the dichroic dye (D5) in the liquid crystal film were evaluated, the dichroic ratio was 1.9 and the order parameter was 0.23. Compared to the case where the same dichroic dye (D5) was added to the liquid crystal film containing the polymerizable liquid crystal compound (A), the order parameter ratio was 0.67 times. Further, the molecular length of the dichroic dye (D5) excluding the terminal alkyl chain was evaluated by the same method as in Reference Example 2, and it was 1.73 nm.

(Comparative Example 3)
Instead of the dichroic dye (D1), the dichroic dye (D6) represented by the following formula (maximum absorption wavelength 540 nm) is 0.204 weight per 100 parts by weight of the polymerizable liquid crystal composition (B). An optical film (6) (liquid crystal film / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that a part thereof was added.

When the wavelength dispersion characteristic of the optical film (6) was measured, Δn · d at 550 nm was 141.2 nm, and Δn · d (500) / Δn · d (550) = 0.980, Δn · d (580 ) / Δn · d (550) = 1.010. The average tilt angle of the liquid crystal film was 24 degrees, and the tilt angle at the interface on the TAC film side was 45 degrees.

(Evaluation of dichroic ratio of pigment)
Except for using the dichroic dye (D6) in place of the dichroic dye (D1), it has “positive dispersion” characteristics comprising the polymerizable liquid crystal compound (A) in the same manner as in Reference Example 2. When the dichroic ratio and order parameter (S) of the dichroic dye (D1) in the liquid crystal film were evaluated, the dichroic ratio was 4.0, and the order parameter was 0.50.

  Except for using the dichroic dye (D6) in place of the dichroic dye (D1), the “negative dispersion” characteristic comprising the polymerizable liquid crystal composition (B) was obtained in the same manner as in Reference Example 3. When the dichroic ratio and order parameter (S) of the dichroic dye (D6) in the liquid crystal film were evaluated, the dichroic ratio was 2.1 and the order parameter was 0.27. When compared with the case where the dichroic dye (D6) was added to the liquid crystal film containing the polymerizable liquid crystal compound (A), the order parameter ratio was 0.55. Further, the molecular length of the dichroic dye (D6) excluding the terminal alkyl chain was evaluated by the same method as in Reference Example 2, and it was 1.59 nm.

(Comparative Example 4)
An optical film (7) (liquid crystal film / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that the dichroic dye was not added.

  When the wavelength dispersion characteristic of the optical film (7) was measured, Δn · d at 550 nm was 143 nm, Δn · d (500) / Δn · d (550) = 0.981, Δn · d (580) / Δn · d (550) = 1.09. The average tilt angle of the liquid crystal film was 24 degrees, and the tilt angle at the interface on the TAC film side was 45 degrees.

(Comparative Example 5)
In the same manner as in Reference Example 3, except that the addition amount of the dichroic dye (D1) was 0.065 parts by weight with respect to 100 parts by weight of the polymerizable liquid crystal composition (B), an optical film ( 8) (liquid crystal film / adhesive layer / TAC film) was obtained.

When the birefringence wavelength dispersion characteristic of the optical film (8) was measured, Δn · d at 550 nm was 140.9 nm, and Δn · d (500) / Δn · d (550) = 0.978, Δn · d (580) / Δn · d (550) = 1.010. Moreover, it was a homogeneous alignment film, the average tilt angle of the liquid crystal film was 0.4 degree, and the tilt angle at the TAC film side interface was 0.1 degree.

  Optical films (1) to (8) (liquid crystal film / adhesive layer / TAC film), commercially available polarizing plate 1 (manufactured by Sumitomo Chemical Co., Ltd., trade name: SRW062), absorption axis 2 of polarizing plate 1, The circularly polarizing plate 7 was produced by bonding together with an acrylic pressure-sensitive adhesive so that the tilt direction 5 of the liquid crystal film 4 in the optical film 3 was 45 degrees. At the time of bonding, the TAC film 6 side was laminated so as to be in contact with the polarizing plate 1. FIG. 11 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 1 and the liquid crystal film 4 of the optical film 3. In the liquid crystal film 4 in the optical film 3, the surface on which the liquid crystal compound rises is on the side of the polarizing plate 1, and the surface on which the liquid crystal compound lies 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 an organic EL display device.

Evaluation (A): Evaluation of the effect of preventing external light reflection during frontal observation In a state where no voltage is applied to the organic EL element, it is placed in an environment with an illuminance of about 100 lux, and the reflection color blackness of the laminated polarizing plate bonding portion is Sensory evaluation was performed. It was confirmed which black level corresponds to any of the following four levels.
1: There is almost no external light reflection and the color is black.
Although inferior to 2: 1, external light reflection is sufficiently suppressed, and the color is almost black.
3: A little external light reflection is visually recognized.
4: External light reflection is extremely visually recognized.

Evaluation (B): Evaluation of viewing angle characteristics of the effect of preventing reflection of external light With no voltage applied to the organic EL element, it is placed in an environment with an illuminance of about 100 lux, The blackness of the reflected color was sensory evaluated. It was confirmed which black level corresponds to any of the following four levels.
1: Almost no change in external light reflection is seen between the front and diagonal directions.
Although it is inferior to 2: 1, the difference in external light reflection between the front and the diagonal direction is slight.
3: A difference in external light reflection is recognized between the front and the diagonal direction.
4: A considerable difference in external light reflection is recognized between the front and diagonal directions.

Evaluation (C): Evaluation of reduction in luminance of organic EL element The front luminance when the organic EL display device bonded with the laminated polarizing plate is lit in white at a specified luminance is a spectral radiometer SR-3A manufactured by Topcon Corporation. It was measured. Based on Comparative Example 5, how much the luminance of each Example and Comparative Example was reduced was expressed as a percentage. The spectrum of white light is as shown in FIG.

Table 3 shows the evaluation results of (A), (B), and (C) described above.
As shown in Table 2, the laminated polarizing plate provided with the optical films obtained in Examples 1 to 3 and Comparative Examples 1 to 3 is excellent in the effect of preventing reflection of external light during front observation, and also has good viewing angle characteristics. there were.
On the other hand, the laminated polarizing plate provided with the optical film obtained by Comparative Example 4 that does not contain a dichroic dye, when viewed from the front and the oblique direction, the external light reflection is visually recognized, and the color is also bluish. It was.
Moreover, although the laminated polarizing plate provided with the liquid crystal film containing the liquid crystal compound with homogeneous alignment obtained by the comparative example 5 was recognized as the external light reflection preventing effect at the time of front observation, The difference was considerably recognized, and it was confirmed that the tint change in the oblique direction was strong blue.
Moreover, although the laminated polarizing plate provided with the optical film obtained by Comparative Examples 1 to 3 is equivalent to Examples 1 to 3 in the antireflection effect, the order parameter ratio of the dichroic dye is low. Was confirmed to be lower than those of Examples 1 to 3.

Claims (8)

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 polymerizable liquid crystal composition containing a liquid crystal compound and a dichroic dye, and the liquid crystal compound is nematic hybrid aligned,
A retardation plate represented by the following formula (1), wherein the order parameter (S) of the dichroic dye in the retardation plate is in the range of 1.0 ≧ S ≧ 0.5.
S = (DR-1) / (DR + 2) (1)
(In the formula (1), DR represents the following formula (2):
(In the formula (2), λ represents the wavelength (nm) of light in vacuum,
Ae (λ) represents a polarization absorption spectrum parallel to the slow axis in the retardation plate,
Ao (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the retardation plate,
Ae0 (λ) represents a polarization absorption spectrum parallel to the slow axis in the retardation plate excluding the dichroic dye,
Ao0 (λ) represents a polarization absorption spectrum perpendicular to the slow axis in the retardation plate excluding the dichroic dye. The dichroic ratio of the dichroic dye represented by )   The retardation plate according to claim 1, wherein the dichroic dye is a rod-like molecule, and a molecular length in a major axis direction is 2 to 10 nm.   The phase difference plate according to claim 1 or 2, wherein a content of the dichroic dye is 0.03 to 0.8 parts by weight with respect to 100 parts by weight of the polymerizable liquid crystal composition.   The phase difference plate as described in any one of Claims 1-3 whose maximum absorption wavelength of the said dichroic dye is 380-780 nm.   The phase difference plate as described in any one of Claims 1-4 whose order parameter ratio of the said dichroic dye is 0.7-1.2.   The laminated polarizing plate provided with the phase difference plate as described in any one of Claims 1-5, and a polarizer.   The display apparatus provided with the phase difference plate as described in any one of Claims 1-5.   The display device according to claim 7, wherein the maximum absorption wavelength of the dichroic dye contained in the retardation plate is different from the maximum wavelength of the emission spectrum of the display device.