JP2015161714A - Retardation plate, elliptical polarization plate, and display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a retardation plate consisting of a single sheet, which has desired birefringence wavelength dispersion characteristics in a single film state and can be easily produced by coating, and to provide an image display device, a liquid crystal display device, and an organic electroluminescence display device having wide view angle characteristics using the retardation plate.SOLUTION: The retardation plate comprises a polymerizable liquid crystal compound. The retardation plate comprises a liquid crystal film that shows a "negative dispersion" characteristic with the larger birefringence Δn at the longer measurement wavelength in a given wavelength region of a visible light region, and that has a fixed nematic hybrid alignment structure or a twist nematic hybrid alignment structure.

Description

  The present invention relates to a retardation plate and an elliptically polarizing plate used for a liquid crystal display device, an organic electroluminescence display device, and the like, and an image display device, a liquid crystal display device, an organic electroluminescence display device and the like using the same. About.

  The phase difference plate is an optical element used to obtain polarized light (linearly polarized light, circularly polarized light, elliptically polarized light), and is used for color compensation of liquid crystal display devices and viewing angle improving films. Is used in many applications such as a reflection type polarizing plate for reflecting only the right or left-handed circularly polarized light composed of cholesteric liquid crystal or the like. A retardation plate is a plate obtained by thinly cutting an inorganic material (calcite, mica, crystal), a film obtained by stretching a polymer film having a high intrinsic birefringence, or a film obtained by aligning and fixing a rod-like or disc-like liquid crystal material in a 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 has an optical function of converting linearly polarized light into circularly polarized light. The half-wave plate has a function of converting the polarization vibration plane of linearly polarized light by 90 °.

  The retardation plate is usually designed so as to exhibit a necessary optical function with respect to light of a specific wavelength (monochromatic light). However, the above-described color compensation film for liquid crystal display device and organic EL display device Quarter-wave plates used in antireflection films for light conversion of linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light at a measurement wavelength (λ) of 400 to 700 nm, preferably 400 to 780 nm in the visible light region It is necessary to have an action to If this is to be realized with a single retardation plate, the phase difference is that the phase difference becomes a quarter wavelength of the measurement wavelength, that is, λ / 4 (nm) at a measurement wavelength of 400 to 700 nm, preferably 400 to 780 nm. The ideal of the board.

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

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

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

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

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

  Patent Document 4 discloses a retardation obtained by uniaxially stretching a mixture or copolymer film of at least two kinds of organic polymers composed of an organic polymer having positive birefringence and an organic polymer having negative birefringence. A retardation plate having a “negative dispersion” characteristic with a single film is disclosed. The retardation film described in Patent Document 4 will be described with reference to a schematic diagram as shown in FIG. 4 and a graph of birefringence wavelength dispersion characteristics as shown in FIG. When an extraordinary ray refractive index ne1 and an ordinary ray refractive index no1 of an organic polymer having “positive birefringence” (denoted by rod-like molecule 1 in FIG. 4), birefringence Δn1 (= ne1−no1)> 0. . When an extraordinary ray refractive index ne2 and an ordinary ray refractive index no2 of an organic polymer having “negative birefringence” (denoted by a discotic molecule 3 in FIG. 4), Δn2 (= ne2−no2) <0. Here, in the case of combining materials in which the birefringence Δn1 of the organic polymer having “positive birefringence” is larger than the birefringence Δn2 of the organic polymer having “negative birefringence” (that is, Δn1> Δn2) Case), the total birefringence Δn = Δn1 + Δn2> 0, and the mixture is “positive birefringence”. Further, the chromatic dispersion characteristic D1 of the birefringence Δn1 of the organic polymer having “positive birefringence” is expressed as D1 = Δn1 (450) / Δn1 (650) (where Δn1 (450) and Δn1 (650) are The birefringence of the polymer film at the measurement wavelengths of 450 nm and 650 nm, respectively.), And the wavelength dispersion characteristic D2 of the birefringence Δn2 of the organic polymer having “negative birefringence”, D2 = Δn2 (450) / Δn2 ( 650) (where Δn2 (450) and Δn2 (650) are the birefringence of the polymer film at the measurement wavelengths of 450 nm and 650 nm, respectively), as shown in FIG. When the wavelength dispersion characteristic D2 of the organic polymer having “birefringence” is designed to be larger than the wavelength dispersion characteristic D1 of the organic polymer having “positive birefringence” (that is, D2> 1), as the mixture, a phase difference plate having a "positive birefringence" and "negative dispersion" characteristics.

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

  Patent Document 5 discloses a liquid crystal film made of a rod-like liquid crystal compound as a retardation plate that is a thin film and has a measurement wavelength that increases as the wavelength increases. The retardation plate described in Patent Document 5 is a homogeneous alignment of a liquid crystal compound containing a compound having two or more kinds of mesogenic groups and rod-like liquid crystal molecules, and at least one kind of mesogenic group is relative to the optical axis direction of the rod-like liquid crystal compound, Utilizing the orientation in a substantially orthogonal direction is utilized. The rod-like liquid crystal compound has a relatively large birefringence Δn compared to the copolymer resin, and therefore has a thickness of several μm, which is advantageous in terms of thinning the retardation plate.

However, the circularly polarizing 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. Light incident from the direction is converted into elliptically polarized light that is greatly deviated from circularly polarized light, narrowing the viewing angle of the display in a liquid crystal display device, or light leakage in an oblique direction in an antireflection film in an organic EL display device May occur.
Patent Document 6 discloses a circularly polarizing plate in which a birefringent material of NZ <0 is provided between a polarizer and a quarter wavelength plate. Here, NZ is NZ = (nx-nz) / nx-ny) (where nx and ny represent the in-plane main refractive index with respect to light having a wavelength of 550 nm, and nx ≧ ny is satisfied. It represents the main refractive index in the thickness direction for light of 550 nm. The circularly polarizing plate described in Patent Document 7 compensates for the viewing angle dependency of the phase difference by providing a birefringent body with NZ <0, and improves the viewing angle characteristics of the circularly polarizing plate. There are adverse effects such as cost increase and thickness increase by using a special material of 0.
Patent Documents 7 and 8 disclose a circularly polarizing plate made of a liquid crystal film in which a polarizing plate and a nematic hybrid alignment structure having a phase difference of approximately a quarter wavelength are fixed. It has been proposed as a method of widening the viewing angle of a display in a transmissive or reflective liquid crystal display device by a circularly polarizing plate comprising a quarter wavelength plate having a nematic hybrid alignment structure and a polarizing plate. In order to achieve a four-wave plate, a combination with a half-wave plate made of a polymer stretched film is necessary, and an increase in cost and thickness is inevitable.

JP-A-10-68816 JP-A-10-90521 Japanese Patent Laid-Open No. 11-52131 JP 2002-48919 A JP 2002-267838 A JP 2005-326818 A JP 2002-31717 A JP 2000-321576 A

  An object of the present invention has been made in view of the above-described situation, and is a retardation film having a desired birefringence wavelength dispersion characteristic with a single film, an elliptically polarizing plate using the retardation plate, and a wide viewing angle image display device. Is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have optimized the birefringence wavelength dispersion characteristics of the polymerizable liquid crystal compound and optimized the film production conditions, so that the birefringence Δn is visible light. In a certain wavelength region, a novel phase difference plate was found in which a nematic hybrid alignment structure having a “negative dispersion” characteristic that becomes larger as the measurement wavelength is longer is fixed. That is, the present invention is as follows.

[1] A liquid crystal film having a “negative dispersion” characteristic in which the birefringence Δn increases in the visible light region as the measurement wavelength becomes longer, and the retardation plate has a nematic hybrid alignment structure fixed thereto. A phase difference plate comprising:

[2] A phase difference plate having a “negative dispersion” characteristic in which the birefringence Δn increases in the visible light region as the measurement wavelength is longer, and the phase difference plate is a liquid crystal in which a twisted nematic hybrid alignment structure is fixed. A phase difference plate comprising a film.

[3] The liquid crystal film according to [1], wherein the liquid crystal film is a liquid crystal film in which a polymerizable liquid crystal compound is nematic hybrid aligned in a liquid crystal state and the alignment is fixed by a crosslinking reaction by light or heat. Phase difference plate.
[4] The liquid crystal film according to [2], wherein the liquid crystal film is a liquid crystal film in which a polymerizable liquid crystal compound is twisted nematic hybrid aligned in a liquid crystal state and the alignment is fixed by a crosslinking reaction by light or heat. Phase difference plate.

[5] In any one of the above [1] to [4], the retardation ratio in the normal direction of the retardation plate at a specific wavelength satisfies the following formulas (1) and (2): The retardation plate described.
0.80 <Δn · d (500) / Δn · d (550) <1.00 (1)
1.00 <Δn · d (600) / Δn · d (550) <1.15 (2)
(Here, retardation is represented by the product of birefringence Δn and the film thickness d of the retardation plate, and Δn · d (500), Δn · d (550), and Δn · d (600) are respectively wavelengths. Retardation of retardation plate at 500 nm, 550 nm, and 600 nm.)

[6] The retardation plate according to any one of [1] to [5], wherein an average tilt angle of liquid crystal molecules of the liquid crystal film is 10 ° to 45 °.
[7] The retardation plate according to any one of [1] to [6], wherein a twist angle in a film plane of liquid crystal molecules of the liquid crystal film is 0 ° to 90 °.
[8] An elliptically polarizing plate comprising the retardation plate according to any one of [1] to [7] and a polarizing plate bonded together.
[9] An image display device in which the elliptically polarizing plate according to [8] is disposed.
[10] A liquid crystal display device on which the elliptically polarizing plate according to [8] is disposed.
[11] An organic electroluminescence display device in which the elliptically polarizing plate according to [8] is disposed.

  According to the present invention, by optimizing the birefringence wavelength dispersion characteristics of an organic polymer, a retardation plate having a “negative dispersion” characteristic in which the birefringence Δn increases as the measurement wavelength increases in the visible light region. Made possible. In addition, by optimizing the film production conditions, it was possible to create a new retardation plate with a fixed nematic hybrid alignment structure. A retardation plate having such a liquid crystal alignment structure and birefringence wavelength dispersibility and having a phase difference of 1/4 wavelength at a measurement wavelength of 550 nm makes circularly polarized light linearly polarized in a wide wavelength region in the front and oblique directions. Furthermore, since it functions as a phase difference plate that converts linearly polarized light into circularly polarized light, when used in a liquid crystal display device, display characteristics such as brightness and contrast ratio are improved in the front and oblique directions, and the organic electroluminescence display device is improved. If used, the high prevention performance against specular reflection is greatly improved at a wide viewing angle.

It is a figure which shows the comparison with the wavelength dispersion of a general polymer film and ideal birefringence (DELTA) n. It is a figure which shows the polymer film 2 which consists of the organic polymer (rod-shaped molecule) 1 which has positive birefringence. It is a figure which shows the comparison with the wavelength dispersion of the extraordinary ray refractive index ne and the ordinary ray refractive index no of the rod-shaped molecule | numerator which has anisotropy. It is a figure which shows the polymer film 2 which consists of the organic polymer (rod-shaped molecule) 1 which has positive birefringence, and the organic polymer (disk-shaped molecule) 3 which has negative birefringence. It is a figure explaining that birefringence expresses a "negative dispersion" characteristic by the polymer film which consists of an organic polymer which has positive birefringence, and an organic polymer which has negative birefringence. It is a figure which shows the comparison with the phase difference plate which has a "negative dispersion | distribution" characteristic, and ideal birefringence wavelength dispersion. It is a conceptual diagram of the orientation structure of a nematic hybrid liquid crystal film. It is a conceptual diagram for demonstrating the tilt angle and twist angle of a liquid crystal molecule. It is a figure which shows the wavelength dispersion characteristic of birefringence (DELTA) n of the liquid crystal film produced in Example 1, Example 2, Example 3, Example 4, and the comparative example 1. FIG. It is a measurement result of the apparent retardation value measured by inclining the liquid crystal film produced in Example 1 along the alignment direction of a liquid crystal. 3 is a diagram illustrating a layer configuration of a circularly polarizing plate manufactured in Example 1 and Comparative Example 2. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in Example 1 is mounted in an organic electroluminescence display. 6 is a diagram showing a layer structure of a circularly polarizing plate produced in Example 2. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in Example 2 is mounted in an organic electroluminescence display. It is a measurement result of the apparent retardation value measured by inclining the liquid crystal film produced in Example 3 along the alignment direction of a liquid crystal. 6 is a diagram showing a layer structure of a circularly polarizing plate produced in Example 2. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in Example 2 is mounted in an organic electroluminescence display. 4 is a diagram illustrating a layer configuration of a circularly polarizing plate manufactured in Example 3. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in Example 3 is mounted in an organic electroluminescence display. 6 is a diagram showing a layer configuration of a circularly polarizing plate manufactured in Comparative Example 1. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all directions when the circularly-polarizing plate produced in the comparative example 1 is mounted in an organic electroluminescence display. It is a figure which shows the wavelength dispersion characteristic of birefringence (DELTA) n of the liquid crystal film produced in the comparative example 2. FIG. It is the figure which measured the viewing angle characteristic of the reflectance when it sees from all the directions when the circularly-polarizing plate produced in the comparative example 2 is mounted in an organic EL display apparatus.

Hereinafter, the present invention will be described in detail.
The retardation plate of the present invention is a retardation plate comprising a liquid crystal film in which a nematic hybrid alignment structure is fixed to a polymerizable liquid crystal compound, and birefringence Δn has a long measurement wavelength in the visible light region. It is a retardation plate having a “negative dispersion” characteristic that becomes larger as it becomes larger.

The retardation plate of the present invention is a retardation plate having a “negative dispersion” characteristic in which the birefringence Δn increases in the visible light region as the measurement wavelength increases. The visible light region generally represents a region of 380 nm to 780 nm. More specifically, the retardation of the polymer film at 500 nm, 550 nm, and 600 nm is Δn · d (500), Δn · d (550). , Δn · d (600),
0.80 <Δn · d (500) / Δn · d (550) <1.00 (1)
And 1.00 <Δn · d (600) / Δn · d (550) <1.15 (2)
It is preferable that Here, the retardation is represented by the product (Δn · d) of birefringence Δn and the thickness d of the retardation plate. More preferably, 0.90 <Δn · d (500) / Δn · d (550) <0.98 (1-1)
And 1.02 <Δn · d (600) / Δn · d (550) <1.10 (2-1)
It is. When deviating from these values, for example, when used as a quarter wave plate, when linearly polarized light of 400 to 700 nm is incident on this film, the polarization state obtained is a perfect circle at a specific wavelength. Although polarized light can be obtained, there is a problem that it is greatly deviated from circularly polarized light at other wavelengths.

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

  In addition, the retardation plate of the present invention is composed of a liquid crystal film in which a nematic hybrid alignment structure is fixed. FIG. 7 shows a cross-sectional structure of a liquid crystal film having a nematic hybrid alignment structure of the present invention. In a film having a nematic hybrid alignment structure, the director of the polymerizable liquid crystal compound is oriented at different angles at all positions in the film thickness direction. Accordingly, the retardation plate of the present invention no longer has an optical axis when viewed as a film structure. FIG. 8 shows definitions of the tilt angle and twist angle of liquid crystal molecules. Here, the tilt direction (axis) of the liquid crystal film refers to a liquid crystal molecule director and a projection component onto the c plane of the director when the c plane is viewed from the b plane through the liquid crystal film as shown in FIG. A direction in which the angle is an acute angle and parallel to the projection component is defined as a tilt direction (axis).

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

The retardation plate of the present invention may be a liquid crystal film in which a twisted nematic hybrid alignment structure is fixed. A liquid crystal film in which twisted nematic alignment is fixed has a structure in which a director of liquid crystal molecules twists an optically anisotropic axis from one surface to the other surface. Therefore, this retardation plate has characteristics equivalent to those obtained by stacking optically anisotropic layers in multiple layers so that the optical anisotropic axis is continuously twisted, and is a normal TN (twisted nematic). ) Like liquid crystal cells and STN (super twisted nematic) liquid crystal cells, the retardation value (= Δnd: value represented by the product of birefringence Δn and thickness d) and twist when viewed from the normal direction of the film Has horns. Furthermore, the liquid crystal film with a fixed twisted nematic hybrid alignment structure is different in the film thickness direction, while the director of the liquid crystal molecules is twisted in the in-plane direction from one side to the other side of the liquid crystal molecule. It is a film inclined at an angle. The twist angle in the orientation structure is usually 0 ° to 90 °, preferably 0 ° to 70 °, and most preferably 0 ° to 60 ° as an absolute value. When the twist angle deviates more than 90 °, when the liquid crystal display device or organic EL display device is provided in combination with a polarizing plate, the contrast, antireflection performance, etc., display characteristics when viewed from the front, etc. There is a fear. Here, although there are two types of twist angles, the twist angle may be either the right twist or the left twist.
Such retardation value, twist angle, and tilt angle can be measured by a device capable of measuring birefringence (for example, trade name “Axoscan” manufactured by Axometrics, trade name “KOBRA-21ADH” manufactured by Oji Scientific Instruments, etc.) ) Can be calculated from the value measured using
The retardation plate of the present invention is a liquid crystal film in which a solution in which a polymerizable liquid crystal compound is dissolved in an appropriate solvent is applied and dried, and then alignment is fixed in a liquid crystal state.

  Hereinafter, the retardation film made of the liquid crystal film used in the present invention will be described in order.

The liquid crystal film is a film obtained by aligning and fixing a polymerizable liquid crystal polymer in a liquid crystal state. The orientation of the liquid crystal film here refers to a state in which the molecular chains of the polymerizable liquid crystal compound are aligned in a specific direction, and this state can be measured by measuring the phase difference (Δn · d) of the film. For example, the orientation in FIG. 4 indicates that Δn · d is 20 nm or more at a measurement wavelength of 550 nm. Δn · d is the product of birefringence Δn and film thickness d.
The polymerizable liquid crystal material that is a constituent component of the retardation film made of the liquid crystal film of the present invention will be described.

  Such a polymerizable liquid crystal compound is not particularly limited as long as it is a liquid crystal compound capable of fixing the alignment state by polymerization, and a known polymerizable liquid crystal compound can be appropriately used. Moreover, as such a polymerizable liquid crystal compound, it is preferable to use a polymerizable liquid crystal compound that can be nematic hybrid aligned on a substrate to fix the alignment state. Furthermore, as such a polymerizable liquid crystal compound, for example, a low molecular weight polymerizable liquid crystal compound (a liquid crystalline monomer having a polymerizable group), a high molecular weight polymerizable liquid crystal compound (a liquid crystalline polymer having a polymerizable group), And mixtures thereof can be used as appropriate.

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

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

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

In the general formulas (10) to (12), W independently represents any one of H and CH ₃ . Depending on the type of W, a group represented by CH ₂ = CWCOO in the formula is either an acrylate group or a methacrylate group.
Moreover, in formula (10)-(12), n is an integer of 1-20 (more preferably 2-12, still more preferably 3-6). If the value of n is less than the lower limit, the temperature range in which the compound exhibits liquid crystallinity tends to be small. On the other hand, if it exceeds the upper limit, the liquid crystal derived from the compound is necessary to realize good parallel alignment. As a result of the decrease in fluidity, it tends to be difficult to achieve good parallel orientation.

In the general formula (10), R ^a is any group selected from an alkyl group having 1 to 20 carbon atoms and an alkoxy group having 1 to 20 carbon atoms. Such an alkyl group having 1 to 20 carbon atoms that can be selected as ^Ra is preferably one having 1 to 12 carbon atoms, and more preferably 3 to 6 carbon atoms. When the number of carbons exceeds the above upper limit, the liquidity derived from the liquid crystal of the compound necessary for realizing a good nematic hybrid alignment tends to be reduced, so that it is difficult to realize a good nematic hybrid alignment. . Moreover, when the carbon number is less than the lower limit, the temperature range in which the compound exhibits liquid crystallinity tends to be small. Such an alkyl group may be linear, branched, or cyclic, and is not particularly limited, but it can realize a good nematic hybrid orientation. From a viewpoint, it is more preferable that it is a linear thing.
Moreover, as for the C1-C20 alkoxy group which can be selected as said Ra, ^a C1-C12 thing is more preferable, and a C3-C6 thing is still more preferable. When the number of carbons exceeds the above upper limit, the liquidity derived from the liquid crystal of the compound necessary for realizing a good nematic hybrid alignment tends to be reduced, so that it is difficult to realize a good nematic hybrid alignment. . Moreover, when the carbon number is less than the lower limit, the temperature range in which the compound exhibits liquid crystallinity tends to be small. The alkoxy group has a structure in which an alkyl group is bonded to an oxygen atom. The structure of the alkyl group portion may be linear, branched, or cyclic. Although it may be sufficient and it does not restrict | limit, From a viewpoint of implement | achieving favorable nematic hybrid orientation, it is more preferable that it is a linear thing.

In the general formula (12), Z ¹ and Z ² are each independently any group of —COO— and —OCO—. Such Z ¹ and Z ² are groups in which ^one of Z ¹ and Z ² is represented by —COO—, and the other group is — A group represented by OCO- is preferable. Further, in the general formula (12), ^{X 1} and ^{X 2} are each independently, H, and carbon atoms exhibits any of the alkyl group having 1 to 7. The alkyl group having 1 to 7 carbon atoms that can be selected as X ¹ and X ² is more preferably 1 to 3 carbon atoms, and the alkyl group is 1 (the alkyl group is CH ₃ . Is more preferable. If the number of carbon atoms exceeds the above upper limit, it tends to be difficult to realize a good nematic hybrid orientation. Thus, it is particularly preferable that X ¹ and X ² are each independently one of H and CH ₃ .

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

The polymerizable liquid crystal compound is preferably used in combination with the compounds represented by the general formulas (10) to (12), and is combined with the compounds represented by the general formulas (110) to (113). It is more preferable to use it.
Thus, in the case where the compounds represented by the general formulas (10) to (12) are combined and used as the polymerizable liquid crystal compound, the content of the compound represented by the general formula (10) It is preferably 20 to 60% by mass, more preferably 30 to 45% by mass, based on the total amount of the compounds represented by formulas (10) to (12). When the content of the compound represented by the general formula (10) is less than the lower limit, an orientation defect tends to occur with respect to the nematic hybrid orientation. On the other hand, when the content exceeds the upper limit, there is an orientation defect with respect to the nematic hybrid orientation. Tend to occur.

  In the case where the compounds represented by the general formulas (10) to (12) are used in combination, the content of the compound represented by the general formula (11) is represented by the general formulas (10) to (12). It is preferable that it is 10-50 mass% with respect to the total amount of the compound represented, and it is more preferable that it is 20-30 mass%. When the content of the compound represented by the general formula (11) is less than the lower limit, an orientation defect tends to occur with respect to the nematic hybrid orientation. On the other hand, when the content exceeds the upper limit, the orientation defect has an orientation defect with respect to the nematic hybrid orientation. Tend to occur.

  Further, when the compounds represented by the general formulas (10) to (12) are used in combination, the content of the compound represented by the general formula (12) is represented by the general formulas (10) to (12). It is preferable that it is 10-70 mass% with respect to the total amount of the compound represented, and it is more preferable that it is 25-45 mass%. When the content of the compound represented by the general formula (12) is less than the lower limit, an orientation defect tends to occur with respect to the nematic hybrid orientation. On the other hand, when the content exceeds the upper limit, there is an orientation defect with respect to the nematic hybrid orientation. Tend to occur.

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

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

In the present invention, the phase difference Δn · d needs to satisfy the following expressions (1) and (2).
0.80 <Δn · d (500) / Δn · d (550) <1.00 (1)
1.00 <Δn · d (600) / Δn · d (550) <1.15 (2)
In particular, as a method of satisfying 0.80 <Δn · d (500) / Δn · d (550) <1.00, the polymerizable polymer compound is a compound having two or more kinds of mesogenic groups, and at least one of them. By aligning one mesogenic group in a direction substantially orthogonal to the slow axis of the homogeneous alignment of the liquid crystal layer, the longer the wavelength, the greater the phase difference. JP-A-2002-267838 and JP-A-2010- This is described in Japanese Patent No. 31223. Here, the mesogen of the mesogen group is also an intermediate phase (= liquid crystal phase) forming molecule ("Liquid Crystal Dictionary", Japan Society for the Promotion of Science, 142nd Committee on Organic Materials for Information Science, edited by Liquid Crystal Division, 1989) And is almost synonymous with the liquid crystalline molecular structure. In the present invention, it is preferable to employ a mesogenic group in the rod-like liquid crystal (molecular structure relating to liquid crystallinity of the rod-like liquid crystal). The mesogenic group in the rod-like liquid crystal is described in various documents (for example, Flussige Kristalle in Tabellen, VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig (1984), Volume 2).

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

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

A compound having two or more kinds of mesogenic groups can be synthesized by applying a general synthesis method. For example, 1) a sequential introduction method in which one of two or more kinds of mesogenic groups is first introduced by functional group conversion of the starting material, and then another mesogenic group is continuously introduced by functional group conversion; 2) starting material It is possible to adopt a simultaneous introduction method in which two or more kinds of mesogenic groups are simultaneously introduced by the functional group conversion of 3), or a combined method of 3) sequential introduction method and simultaneous introduction method. Thus, the method for producing a compound having two or more kinds of mesogenic groups is not particularly limited, and a known method can be appropriately used. For example, the method described in JP-A-2002-267838 May be adopted. Thus, the polymerizable liquid crystal compound can be produced by appropriately using a known method according to the type of the compound to be used. Moreover, you may utilize a commercial item as such a polymeric liquid crystal compound. Further, such polymerizable liquid crystal compounds may be used singly or in combination of two or more.
In order to induce twisted nematic alignment, a liquid crystal material may be a liquid crystal material in which a chiral agent is added to the material, or various liquid crystal materials having at least one chiral structural unit or a non-liquid crystal material are blended. It is particularly desirable to be.
Examples of the chiral structural unit include optically active 2-methyl-1,4-butanediol, 2,4-pentanediol, 1,2-propanediol, 2-chloro-1,4-butanediol, and 2-fluoro. -1,4-butanediol, 2-bromo-1,4-butanediol, 2-ethyl-1,4-butanediol, 2-propyl-1,4-butanediol, 3-methylhexanediol, 3-methyl Units derived from adipic acid, naproxen derivatives, camphoric acid, binaphthol, menthol or cholesteryl group-containing structural units or derivatives thereof (for example, derivatives such as diacetoxy compounds) can be used. The diols may be either R-form or S-form, and may be a mixture of R-form and S-form. These structural units are merely examples, and the present invention is not limited thereto. In addition, even in the case of oligomers and low-molecular liquid crystals, thermal crosslinking, photocrosslinking, etc. in a state where the alignment is fixed by cooling to below the liquid crystal transition temperature or liquid crystal transition temperature by introducing a crosslinkable group or blending of appropriate crosslinking agents. Those that can be polymerized by the above means are also included in the liquid crystal polymer.

  Moreover, such a polymerizable liquid crystal compound may use a mixture of a liquid crystal compound having a polymerizable group and another polymerizable monomer that does not exhibit liquid crystallinity. Such other polymerizable monomers are not particularly limited as long as they have compatibility with a liquid crystal compound having a polymerizable group and do not cause significant alignment inhibition when the liquid crystal compound is aligned. However, a known polymerizable monomer can be appropriately used, and a suitable monomer may be selected from the known polymerizable monomers according to the design of the target liquid crystal composition. Examples of such other polymerizable monomers include compounds having a polymerizable functional group such as an ethylenically unsaturated group (for example, vinyl group, vinyloxy group, (meth) acryloyl group). In addition, the addition amount of such other polymerizable monomer is 0.5 to 50% by mass with respect to the total amount of the liquid crystal compound having the polymerizable group and the other polymerizable monomer not exhibiting the liquid crystal property. Is preferable, and it is preferable to set it as 1-30 mass%. Further, the number of polymerizable functional groups of such a polymerizable monomer is preferably 2 or more from the viewpoint of sufficiently increasing the polymerization rate and imparting sufficient heat resistance to the obtained liquid crystal film. . Furthermore, the method for producing such a polymerizable monomer is not particularly limited, and a known method can be appropriately used. Moreover, you may utilize a commercial item as such a polymerizable monomer. Even a discotic liquid crystal compound can be used without any problem. As the liquid crystal polymer, those showing optically positive or negative uniaxiality are usually used. These optical characteristics are appropriately selected depending on the function required for the optical anisotropic element. In the case of a liquid crystal polymer layer with twist hybrid nematic alignment, a liquid crystal polymer exhibiting positive uniaxiality is preferably used.

It does not restrict | limit especially as a polymerization initiator, A well-known polymerization initiator can be utilized suitably. As described above, the polymerization initiator can start the polymerization of the polymerizable liquid crystal compound more efficiently according to the type of the polymerizable liquid crystal compound in the composition from among known polymerization initiators. What is necessary is just to select suitably and use.
Moreover, even if such a polymerization initiator is a thermal polymerization initiator (an initiator when utilizing a thermal polymerization reaction), a photopolymerization initiator (an initiator when utilizing light or electron beam irradiation) It may be. As such a polymerization initiator, in the case of using a plastic film or the like as a base material when producing a liquid crystal film, from the viewpoint of preventing the base material and the like from being deformed or altered by heat, It is more preferable to use a photopolymerization initiator. Examples of such photopolymerization initiators include α-carbonyl compounds, acyloin ethers, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, triarylimidazole dimers and p-aminophenyl ketones. And acridine and phenazine compounds and oxadiazole compounds. Examples of such α-carbonyl compounds include α-carbonyl compounds described in US Pat. No. 2,367,661 and US Pat. No. 2,367,670. Examples of the acyloin ether include US Pat. The thing etc. which are described in 2448828 specification are mentioned. Examples of the α-hydrocarbon substituted aromatic acyloin compound include those described in US Pat. No. 2,722,512. Examples of the polynuclear quinone compound include US Pat. No. 3,046,127 and US Pat. No. 2,951,758. And the like described in the specification. Examples of the combination of triarylimidazole dimer and p-aminophenyl ketone include those described in US Pat. No. 3,549,367, and the acridine and phenazine compounds include, for example, Examples described in JP-A-60-105667 and U.S. Pat. No. 4,239,850 are exemplified. Further, examples of the oxadiazole compound include those described in U.S. Pat. No. 4,212,970. .

  In addition, as such a photopolymerization initiator, a commercially available product may be used. For example, a photopolymerization initiator manufactured by Ciba-Geigy (trade name “Irgacure 907”, trade name “Irgacure 651”, trade name) “Irgacure 184”) or a photopolymerization initiator (trade name “UVI6974”) manufactured by Union Carbide may be used as appropriate. Such photopolymerization initiators include those that generate free radicals and those that generate ions upon irradiation with light or an electron beam, and the type and polymerization of the polymerizable liquid crystal compound in the composition. Depending on the reaction conditions, etc., a photopolymerization initiator that generates free radicals (for example, trade name “Irgacure 651” manufactured by Ciba-Geigy) or a photopolymerization initiator that generates ions (for example, Union Carbide) A suitable photopolymerization initiator (trade name “UVI6974”) may be appropriately selected and used.

  Moreover, as content of the said polymerization initiator in the polymeric liquid crystal compound which concerns on this invention, it is preferable that it is 1-10 mass parts with respect to 100 mass parts of said mixtures, and it is more preferable that it is 3-5 mass parts. preferable. When the content of such a polymerization initiator is less than the lower limit, the resulting retardation plate tends to have insufficient curability. On the other hand, when the content exceeds the upper limit, liquid crystal orientation tends to be defective.

Next, the manufacturing method of the phase difference plate which consists of a liquid crystal film of this invention is demonstrated.
The method of producing the retardation plate is not limited to these, but the polymerizable liquid crystal compound and a composition containing various compounds added as necessary are in a molten state or a solution of the composition. Is coated on an alignment substrate to form a coating film, and then the coating film is dried, heat-treated (alignment of liquid crystal) or, if necessary, light irradiation and / or heat treatment (polymerization / crosslinking), etc. By fixing the nematic hybrid alignment using the above-described means for fixing the alignment, an optically anisotropic layer in which the alignment of the liquid crystal is fixed is formed.

Here, the state that “the alignment state is fixed in the state of nematic hybrid alignment” means that in the optically anisotropic layer obtained after polymerizing the polymerizable liquid crystal compound to fix the alignment, nematic hybrid alignment ( A liquid crystal molecule director refers to the fact that the directors are aligned at different positions in every direction of the film thickness direction, and the components derived from the polymerizable liquid crystal compound and the like (preferably Any one of the components derived from the polymerizable liquid crystal compound: the polymerizable liquid crystal compound itself, a composition formed by decomposing the polymerizable liquid crystal compound, and a polymer of the polymerizable liquid crystal compound). It may be fixed in a nematic hybrid alignment state.
The solvent used for preparing the solution is not particularly limited as long as it can dissolve the liquid crystal material of the present invention and can be distilled off under suitable conditions. Generally, ketones such as acetone, methyl ethyl ketone, isophorone, cyclohexanone, and cyclopentanone are used. , Alcohols such as isopropyl alcohol, n-butanol, ether alcohols such as butoxyethyl alcohol, hexyloxyethyl alcohol, methoxy-2-propanol, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 2-methoxyethyl acetate, propylene glycol 1- Glycol ethers such as monomethyl ether 2-acetate, esters such as ethyl acetate and ethyl lactate, phenols such as phenol and chlorophenol, N, N-dimethylform Amides such as amides, N, N-dimethylacetamide, N-methylpyrrolidone, halogenated hydrocarbons such as chloroform, dichloromethane, trichloroethylene, tetrachloroethane, tetrachloroethane, tetrachloroethylene, chlorobenzene, dichlorobenzene, tetrahydrofuran, γ- Heterocycles such as butyrolactone, aromatic hydrocarbons such as benzene, toluene, zylene, methoxybenzene, 1,2-dimethoxybenzene, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc., and mixtures thereof Is preferably used.

  In addition, as such a solvent, from the viewpoint of drying speed suitable for applying the solution so as to obtain a uniform film thickness, ease of handling (harmful to the environment) and solubility in the polymerizable liquid crystal compound, Propylene glycol 1-monomethyl ether 2-acetate, 2-methoxyethyl acetate, toluene, zylene, 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. Further, depending on the type of the base material, corrosion may occur depending on the type of the solvent. Therefore, it is preferable to appropriately select and use a suitable solvent according to the type of the base material.

In addition, as the content of the solvent used in the present invention, the usage method of the composition (for example, when used for forming an optically anisotropic layer, the design of the thickness, the coating method, etc. are also included. It differs depending on the method of use etc.) and cannot be generally specified, but it is preferably 30 to 98% by mass, more preferably 50 to 95% by mass, and 70 to 90% by mass. Is more preferable. If the content of the solvent is less than the lower limit, the amount of the solvent with respect to the polymerizable liquid crystal compound decreases, so that the liquid crystal is deposited during storage, or the viscosity of the mixture is increased and the wetting property is decreased. Therefore, it tends to be difficult to coat at the time of production of the retardation plate. On the other hand, when the upper limit is exceeded, the removal time (drying time) takes longer when the solvent is removed, and the film is produced. Not only is the working efficiency lowered, but when the mixture is coated on a substrate, the flow of the surface becomes intense, so that it tends to be difficult to use the composition for producing a uniform retardation plate. Thus, in this invention, it is preferable that the quantity of components other than a solvent is 5-70 mass% on a mass basis, It is more preferable that it is 10-50 mass%, It is 10-30 mass%. More preferably.
In order to form a uniform coating film on the alignment substrate, a reaction activator, a sensitizer, a surfactant, an antifoaming agent, a leveling agent, and the like may be added to the solution.

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

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

  Examples of the cyclic olefin polymer (COP) include cyclic olefin ring-opening polymers, cyclic olefin addition polymers, random copolymers of cyclic olefins and α-olefins such as ethylene and propylene, and the like. Examples include graft-modified products modified with saturated carboxylic acid and derivatives thereof, and hydrides thereof. Moreover, as such a cyclic olefin, norbornene, its derivative (s), and dicyclopentadiene are preferable.

  Among these, plastic films such as triacetyl cellulose, polycarbonate, norbornene polyolefin and the like used as optical films are awarded. Examples of organic polymer film include norbornene such as ZEONOR (trade name, manufactured by ZEON CORPORATION), ZEONEX (trade name, manufactured by ZEON CORPORATION), Arton (trade name, manufactured by JSR Corporation), etc. A plastic film made of a polymer material having a structure is preferable because it has excellent optical properties. Moreover, as a metal film, the said film formed from aluminum etc. is mentioned, for example.

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

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

  Some of these films exhibit sufficient alignment ability for the liquid crystal substance used in the present invention without performing treatment for expressing the alignment ability again depending on the production method, but the alignment ability is insufficient, or alignment If the film does not show the performance, etc., these films are stretched under appropriate heating if necessary, the film surface is rubbed in one direction with a rayon cloth, etc., so-called rubbing treatment, polyimide, polyvinyl alcohol, silane on the film An alignment film made of a known alignment agent such as a coupling agent is provided and subjected to rubbing treatment. A photo-alignment film is applied on the film, heated at an appropriate temperature, and then irradiated with linearly polarized ultraviolet rays to form the alignment film. You may use the film which expressed the orientation ability by oblique vapor deposition processing, such as a silicon oxide, or combining these suitably. In addition, a metal plate such as aluminum, iron, or copper having various fine grooves on the surface, various glass plates, or the like can be used as the alignment substrate. Among these, in the field of liquid crystals, it is common to perform a rubbing process that rubs the substrate with a cloth or the like. An important setting value that defines the rubbing condition is a peripheral speed ratio. This represents the ratio between the movement speed of the cloth and the movement speed of the substrate when the rubbing cloth is wound around a roll and rubbed while the substrate is rubbed. In the present invention, the peripheral speed ratio is usually 50 or less, more preferably 25 or less, and particularly preferably 10 or less. When the peripheral speed ratio is larger than 50, the effect of rubbing is too strong, and the liquid crystal material cannot be completely aligned, and alignment may be insufficient, leading to characteristic deterioration.

Next, the coating method will be described.
The application method is not particularly limited as long as the uniformity of the coating film is ensured, and a known method can be adopted. Examples thereof include spin coating, die coating, curtain coating, dip coating, and roll coating. Such a coating film varies depending on the content of the solvent in the mixture of the polymerizable liquid crystal compound of the present invention and cannot be generally described. However, the thickness of the coating film before drying (wet film thickness) ) Is preferably 3 to 50 μm, and more preferably 5 to 20 μm. If such a thickness (wet film thickness) is less than the lower limit, it is necessary to increase the concentration of solid content (liquid crystal compound, etc.) in the liquid crystal composition in order to obtain desired optical characteristics. In addition to the difficulty of obtaining a uniform liquid crystal film due to the occurrence of minute precipitation, uniform coating is difficult and the smoothness of the liquid crystal film tends to decrease. Since the concentration of the solid content in the liquid crystal composition for obtaining the characteristics is thin, the drying time after coating tends to be long.

  In the method of applying a liquid crystal material solution, it is preferable to include a drying step for removing the solvent after the application. This drying process varies depending on the polymerizable liquid crystal compound used in the present invention, the kind of the solvent, and the like, and is not generally described, and is not particularly limited. For example, depending on the type of solvent, the solvent can be removed from the coating film even at room temperature (25 ° C.). As described above, a nematic hybrid liquid crystal film can be produced without particular heat treatment depending on the type of solvent. Moreover, as temperature conditions in such a solvent removal process, it is preferable that it is 15-110 degreeC, and it is more preferable that it is 20-80 degreeC. If such a temperature condition is less than the lower limit, cooling equipment may be required and efficient production may be difficult.On the other hand, if the upper limit is exceeded, the base material is distorted by heat and optical characteristics and the like change, There is a tendency that desired optical characteristics cannot be obtained.

Moreover, it does not restrict | limit especially as pressure conditions in this drying process, However, It is preferable that it is 600-1400 hPa, and it is more preferable that it is 900-1100 hPa. When the pressure condition is less than the lower limit, the solvent is rapidly dried and uneven drying tends to occur. On the other hand, when the upper limit is exceeded, the solvent tends to take longer to dry. Although it does not restrict | limit especially as time (drying time) of such a solvent removal process, It is preferable to set it as 10 second-60 minutes, and it is more preferable to set it as 1 minute-30 minutes. If the drying time is less than the lower limit, the solvent is rapidly dried, and the smoothness of the liquid crystal film tends to be reduced (drying unevenness occurs). Tend to decrease. In addition, when using a drying apparatus for such a solvent removal process, control the relative moving speed of the said coating film and drying apparatus so that a relative wind speed may be 60m / min-1200m / min. Is preferred. Any known method can be employed without particular limitation as long as the uniformity of the coating film is maintained. For example, a method such as a heater (furnace) or hot air blowing may be used.
The thickness of the applied film in the dry state is 0.1 μm to 50 μm, preferably 0.2 μm to 20 μm. Outside this range, it is not preferable because the optical performance of the obtained optically anisotropic layer is insufficient or the alignment of the polymerizable liquid crystal compound becomes insufficient.

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

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

Further, in such a light irradiation method, the integrated light irradiation amount is preferably 10 to 2000 mJ / cm ² and more preferably 100 to 1500 mJ / cm ² as the integrated exposure amount at a wavelength of 365 nm. preferable. However, this is not the case when the absorption region of the polymerization initiator and the spectrum of the light source are significantly different, or when the polymerizable liquid crystal compound itself has the ability to absorb light of the light source wavelength. In these cases, an appropriate photosensitizer and two or more polymerization initiators having different absorption wavelengths are mixed from the viewpoint of fixing (curing) the coating film while maintaining the orientation state more efficiently. For example, a method such as use may be employed. Further, the temperature condition at the time of such light irradiation is not particularly limited as long as the polymerizable liquid crystal compound can maintain a nematic hybrid alignment state. A cold mirror or other cooling device may be provided between the substrate and the light source (such as an ultraviolet lamp) so that the surface temperature of the coating film can maintain the range of the liquid crystal temperature during light irradiation.

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

In addition, when the polymerization initiator is such that the function of the initiator is manifested by heat (for example, in the case of a so-called thermal cation generator), the alignment is fixed in a nematic hybrid alignment state by heat treatment. It is preferable to do. The conditions for such heat treatment are not particularly limited, and the temperature conditions may be selected so that the orientation state is sufficiently maintained according to the type of the polymerization initiator, and known conditions are appropriately employed. be able to.
If the base material has low heat resistance, the polymerization initiator that exhibits the function of an initiator by light irradiation is used, and the alignment state of the nematic hybrid alignment is fixed by light irradiation. It is preferable to do.

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

  In this way, by applying the mixture containing the polymerizable liquid crystal compound on the alignment substrate, removing the solvent from the coating film, orienting the polymerizable liquid crystal compound, and fixing the liquid crystal state A liquid crystal film in which the alignment state is fixed in a nematic hybrid alignment state can be formed on the alignment substrate.

  As the alignment substrate, it is not optically isotropic, or the obtained retardation plate is finally opaque in the intended use wavelength region, or the alignment substrate is too thick, which hinders actual use. When there is a problem such as occurrence, an optically isotropic substrate, a stretched film having a retardation function, or a form directly transferred to a polarizing plate can be used from the form formed on the alignment substrate. As a transfer method, a known method can be adopted. For example, as described in JP-A-4-57017 and JP-A-5-333313, a liquid crystal film is laminated on a substrate different from the alignment substrate via an adhesive or an adhesive, and then, if necessary, an adhesive is used. Examples include a method of transferring only the liquid crystal film by performing a surface curing treatment using an agent or an adhesive and peeling the alignment substrate from the liquid crystal film. The pressure-sensitive adhesive or adhesive used for transfer is not particularly limited as long as it is of optical grade, and generally used ones such as acrylic, epoxy, and urethane can be used. In addition, it is possible to use the liquid crystal film alone as the element, but in order to improve the strength and durability of the liquid crystal film, the retardation plate is covered with a transparent protective layer on one or both sides of the liquid crystal film. It can also be configured. Examples of the transparent protective layer include those obtained by laminating transparent plastic films such as polyester and triacetyl cellulose directly or via an adhesive, resin coating layers, acrylic and epoxy photocurable resin layers, and the like. It is done. When these transparent protective layers are coated on both sides of the liquid crystal film, different protective layers may be provided on both sides. Moreover, as an optically anisotropic element, a liquid crystal film can be directly formed on a polarizing plate, and the elliptically polarizing plate of this invention can be used as it is. For example, after laminating a liquid crystal film on a transparent plastic film such as polyester or triacetyl cellulose used for producing the polarizing film, the polarizing film / transparent plastic film / retardation plate (liquid crystal film) is integrated with the polarizing film. ) Or a polarizing film / phase difference plate (liquid crystal film) / transparent plastic film.

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

  In addition, the thickness of the liquid crystal film (the thickness of the cured film) varies depending on the application and required characteristics, but is preferably 0.1 to 10 μm, and preferably 0.2 to 5 μm. Is more preferable. If the thickness of the liquid crystal film is less than the lower limit, a desired retardation may not be exhibited. On the other hand, if the thickness exceeds the upper limit, the orientation of the liquid crystal tends to decrease or the transmission due to the dye tends to decrease.

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

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

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

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

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

As the protective film, a hard coat layer, an antireflection treatment, an anti-sticking treatment, or a treatment subjected to diffusion or anti-glare treatment can be used.
Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.
Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, roughening by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a method or a compounding method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.
The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the protective film itself, or can be provided separately from the transparent protective layer as an optical layer.

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

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

In addition, when bonding each optically anisotropic layer mutually through an adhesive layer, the film surface can be surface-treated and adhesiveness with an adhesive layer can be improved. The surface treatment means is not particularly limited, and a surface treatment method such as corona discharge treatment, sputtering treatment, low-pressure UV irradiation, or plasma treatment that can maintain the transparency of each optically anisotropic layer can be suitably employed. Among these surface treatment methods, corona discharge treatment is good.
In addition, since the phase difference plate which consists of a liquid crystal film of this invention is a film which fixed the nematic hybrid alignment structure, the upper and lower sides of the said film are not optically equivalent. Therefore, as an elliptically polarizing plate, 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. Although this invention does not limit which film surface of a liquid crystal film is made into a polarizing plate side, it is requested | required for the optical characteristic requested | required of an elliptically polarizing plate, a liquid crystal display device provided with the said elliptically polarizing plate, and an organic electroluminescent display device. In consideration of display characteristics and the like, it is desirable to determine the configuration of the elliptically polarizing plate of the present invention and the arrangement conditions for the liquid crystal display device and the organic EL display device.

[Image display device]
The image display device of the present invention includes the retardation plate of the present invention and an elliptical (circular) polarizing plate including the retardation plate and a polarizing plate. Such an image display device of the present invention is only required to include the retardation plate of the present invention, and the type of the image display device is not particularly limited, such as a liquid crystal display device, an organic EL display device, and a plasma display. Such a known image display device can be used as appropriate. Further, the method of arranging the retardation plate of the present invention on the image display device is not particularly limited, and a known method can be appropriately used.

A liquid crystal display device to which the retardation plate of the present invention is applied will be described.
The liquid crystal display device of the present invention has at least the retardation plate. A liquid crystal display device is generally composed of a polarizing plate, a liquid crystal cell, and a retardation plate, a reflection layer, a light diffusion layer, a backlight, a front light, a light control film, a light guide plate, a prism sheet, and the like. In the present invention, there is no particular limitation except that the 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 other phase difference plates.

The liquid crystal cell is not particularly limited, and a general liquid crystal cell such as a liquid crystal layer sandwiched between a pair of transparent substrates provided with electrodes can be used.
The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate in which the substrate itself has a property of orienting liquid crystals, a transparent substrate in which an alignment film having the property of orienting liquid crystals is provided, but the substrate itself lacks the alignment ability. Either can be used. Moreover, a well-known thing can be used for the electrode of a liquid crystal cell. Usually, it can be provided on the surface of the transparent substrate in contact with the liquid crystal layer, and when a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.
The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystal substances, polymer liquid crystal substances, and mixtures thereof that can constitute various liquid crystal cells. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired.
In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary for forming various types of liquid crystal cells described later.

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

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

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

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

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

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

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

  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. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded. When the angle formed by the absorption axis of the polarizing plate and the slow axis of the quarter-wave plate is p, the circular polarizing plate is formed by combining a linear polarizing plate with a quarter-wave plate. When the retardation plate of the invention is nematic hybrid orientation, it is usually in the range of 40 ° to 50 °, preferably 42 to 48 °, more preferably about 45 °. In a range other than the above, there is a risk of image quality deterioration due to a decrease in the antireflection effect. 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) Microscope observation The alignment state of the liquid crystal was observed with an Olympus BH2 polarizing microscope.
(2) Refractive index Refractive indexes no and ne are measured using spectroscopic ellipsometry (manufactured by Horiba, Ltd., product name “AUTO-SE”) under conditions of a temperature of 20 ° C. ± 2 ° C. and a relative humidity of 60 ± 5%. A spectrum in the wavelength region of 440 to 1000 nm was measured.
(3) Birefringence measurement An automatic birefringence meter Axoscan manufactured by Axometrics was used.
(4) Reflection viewing angle measurement The viewing angle characteristics of the reflectance when viewed from the front and oblique directions of the organic EL display device were measured using a reflection viewing angle measurement device EZ-CONTRAST manufactured by ELDIM.

Example 1
<Preparation of mixed solution of polymerizable liquid crystal compound (A)>
A compound (21) having two or more kinds of mesogenic groups represented by the following formula and a rod-like liquid crystal compound (22) were prepared. Compound (21) and rod-like liquid crystal compound (22) were produced by the method described in JP-A-2002-267838.

Next, 2 parts by weight of the compound (21) and 17.6 parts by weight of the rod-shaped liquid crystal compound (22) were mixed to obtain a first mixture (referred to as a polymerizable liquid crystal compound (A)). . Next, a polymerization initiator (trade name “Irgacure 651” manufactured by Ciba-Geigy, Switzerland, solid at room temperature (25 ° C.)) is added to the first mixture with the polymerizable liquid crystal compound (A). A second mixture (solid) obtained by mixing the polymerizable liquid crystal compound (A) and the polymerization initiator was added at a ratio of 3 parts by mass with respect to 100 parts by mass of the total amount of the above.
Next, the second mixture is dissolved in chlorobenzene (solvent), the insoluble matter is filtered through a polytetrafluoroethylene filter having a pore size of 0.45 μm, and the polymerizable liquid crystal compound (A) and the polymerization initiator are then filtered. And a solvent containing the solvent (third mixture) was obtained. In producing the third mixture, the content of the solvent in the third mixture is 67% by mass, and the total amount of the polymerizable liquid crystal compound (A) and the polymerization initiator is 33% by mass. % Of the solvent was used.

<Production of liquid crystal film>
The alignment substrate was prepared as follows. A polyethylene naphthalate film having a thickness of 38 μm (PEN manufactured by Teijin Limited) was cut into a 15 cm square, and a 5 wt% solution of alkyl-modified polyvinyl alcohol (PVA: manufactured by Kuraray Co., Ltd., MP-203) was used. (A mixed solvent of isopropyl alcohol having a weight ratio of 1: 1) was applied by spin coating, dried on a hot plate at 50 ° C. for 30 minutes, and then heated in an oven at 120 ° C. for 10 minutes. Subsequently, it was rubbed with a rayon rubbing cloth. The film thickness of the obtained PVA layer was 1.2 μm. The peripheral speed ratio during rubbing (moving speed of rubbing cloth / moving speed of substrate film) was 4.
Spin the mixed solution (third mixture) containing the compound (21), the rod-like liquid crystal compound (22), the polymerization initiator and the solvent obtained as described above onto the alignment substrate thus obtained. Coating (coating) was performed by a coating method to form a coating film (wet film thickness: 5 μm), and a laminate of the coating film and the alignment substrate was obtained.
Next, the laminate of the coating film and the alignment substrate was gradually cooled from pressure: 1013 hPa, temperature: 72 ° C. to 62 ° C. over 10 minutes, and the solvent was removed from the coating film by drying (solvent removal step), followed by room temperature. Quenched until.
Next, with respect to the coating film dried by the solvent removal step, using a high-pressure mercury lamp with an illuminance of 15 mW / cm ² , the integrated irradiation amount is 200 mJ / cm ^2, and ultraviolet light (however, Laminate in which the liquid crystal compound is polymerized (cured) to fix the alignment state, and the alignment state is fixed on the alignment substrate. A body (laminated body of liquid crystal film and alignment substrate) was obtained.

Since the polyethylene naphthalate film used as the substrate has a large birefringence and is not preferable as an optical film, the optically anisotropic layer on the obtained alignment substrate is subjected to triacetylcellulose (TAC) via an ultraviolet curable adhesive. ) Transferred to a film (Fuji Film Z-TAC, 40 um). That is, on the cured liquid crystal film layer on the polyethylene naphthalate film, an adhesive is applied to a thickness of 5 μm, laminated with a TAC film, and irradiated with ultraviolet rays from the TAC film side to cure the adhesive. After that, the alignment substrate was peeled off.
When the obtained optical film (liquid crystal film / adhesive layer / TAC film) was observed under a polarizing microscope, it was found that there was no disclination and uniform orientation of the monodomain.

The wavelength dispersion characteristic of retardation (Δnd) in the in-plane direction of the laminate of the TAC film and the liquid crystal film and the TAC film alone was measured using a trade name “Axoscan” manufactured by Axometrix, and the liquid crystal film layer was subtracted from both. The wavelength dispersion characteristics of the birefringence of was measured. FIG. 9 summarizes the birefringence wavelength dispersion characteristics of the liquid crystal film layer, and Table 1 summarizes the optical characteristics results. Δn · d at 550 nm was 138 nm, and Δn · d (500) / Δn · d (550) = 0.98 and Δn · d (600) / Δn · d (550) = 1.01.
Further, the retardation (Δnd) when the obtained optical film was tilted in the rubbing direction (the alignment direction of liquid crystal molecules) was measured using “Axoscan”. The measurement results are shown in FIG. As shown in FIG. 10, it was found that the viewing angle dependency is asymmetrical and tilted. The obtained optical film was confirmed to be a nematic hybrid alignment film, not a uniform tilt alignment, by the method described in Examples of JP-A No. 11-194325. The average tilt angle was 34 degrees.

<Antireflection performance evaluation of organic EL display>
The obtained optical film is made of an acrylic film so that a commercially available polarizing plate 4 (SRW062 manufactured by Sumitomo Chemical Co., Ltd.), the absorption axis 5 of the polarizing plate 4 and the tilt direction 8 of the liquid crystal layer 7 in the optical film 6 are 45 degrees. The circularly polarizing plate 10 was produced by bonding together with an adhesive. At the time of bonding, the TAC film 9 side was laminated so as to be in contact with the polarizing plate 4. FIG. 11 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 4 and the liquid crystal layer 7 of the optical film 6. In the liquid crystal layer in the optical film 6, the surface on which the liquid crystal molecules rise more is on the side of the polarizing plate 4, and the surface on which the liquid crystal molecules lie further is on the side opposite to the polarizing plate 4.
The obtained circularly polarizing plate 10 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, thereby producing the organic EL display device of the present invention. As a result, it was found that an organic EL display device exhibiting a significant effect of preventing reflection of external light and having excellent visibility as compared with the case where the circularly polarizing plate 10 is not disposed can be obtained.
FIG. 12 and Table 1 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident using a reflection viewing angle measuring device EZ-CONTRAST manufactured by ELDIM and the front reflectance.

(Example 2)
<Antireflection performance evaluation of organic EL display>
The optical film produced in Example 1 was placed on a commercially available polarizing plate 4 (SRW062 manufactured by Sumitomo Chemical Co., Ltd.), the absorption axis 5 of the polarizing plate 4 and the tilt direction 8 of the liquid crystal layer 7 in the optical film 6 being 45 degrees. The circularly polarizing plate 11 was produced by pasting together with an acrylic adhesive. At the time of bonding, the layers were laminated so that the liquid crystal layer 7 side was in contact with the polarizing plate 4. FIG. 13 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 4 and the liquid crystal layer 7 of the optical film 6. The hybrid structure is the reverse of the case of Example 1, and the liquid crystal layer 7 in the optical film 6 has a surface on which the liquid crystal molecules lie more on the polarizing plate 4 side and a surface on which the liquid crystal molecules stand more is polarized. On the opposite side of the plate 4.
The obtained circularly polarizing plate 11 was attached to a transparent glass substrate of an organic EL element of a commercially available organic EL display in the same manner as in Example 1 via an acrylic pressure-sensitive adhesive, and the organic EL display device of the present invention was attached. Created. As a result, it was found that an organic EL display device that exhibits a significant effect of preventing reflection of external light and has excellent visibility as compared with the case where no circularly polarizing plate is provided.
In addition, FIG. 14 and Table 1 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident using a reflection viewing angle measuring device EZ-CONTRAST manufactured by ELDIM and the front reflectance.

(Example 3)
<Production of liquid crystal film>
The third mixture prepared in Example 1 was applied by spin coating on an alignment substrate prepared in the same manner as in Example 1, to form a coating film (wet film thickness: 2.5 um). And a laminated body of the alignment substrate was obtained. Since the substrate used on the laminate has a large birefringence with polyethylene naphthalate, the liquid crystal film layer was peeled and transferred to the TAC film in the same manner as in Example 1, and the laminate composed of TAC / adhesive / liquid crystal film. Got the body. When the wavelength dispersion characteristics of retardation (Δn · d) in the front direction of the laminate and the average tilt were measured by measuring the phase difference in the oblique direction, Δn · d at a wavelength of 500 nm was 69 nm, and the average tilt angle was 34 degrees. Thus, the birefringence wavelength dispersion characteristics coincided with the graph (FIG. 9) of the optical film produced in Example 1.
Further, a second PVA layer was formed on the liquid crystal coating film of the laminate by the same method as in Example 1, and an alignment treatment was performed by rubbing in a direction antiparallel to the first PVA layer. The film thickness of the obtained PVA layer was 1.2 μm. On the PVA layer thus obtained, the third mixture prepared in Example 1 was applied by the same method by spin coating, solvent removal by drying, and ultraviolet light irradiation were performed to obtain a liquid crystal film / PVA alignment film. A laminate comprising: / liquid crystal film / PVA alignment film / PEN substrate was obtained. Furthermore, it transferred to the TAC film by the same method as in Example 1 to obtain a laminate composed of TAC / adhesive / liquid crystal film / PVA alignment film / liquid crystal film. The wavelength dispersion characteristic of retardation (Δnd) in the in-plane direction of the obtained liquid crystal film laminate and the TAC film alone was measured using a trade name “Axoscan” manufactured by Axometrix, and the liquid crystal film layer was subtracted from both. The wavelength dispersion characteristics of the birefringence of was measured. Δn · d at a wavelength of 550 nm was 138 nm, and the chromatic dispersion characteristics coincided with the graph of the optical film produced in Example 1 (FIG. 9).
FIG. 15 shows the measurement results of retardation (Δnd) when the obtained optical film is tilted in the rubbing direction (the alignment direction of liquid crystal molecules). As shown in FIG. 15, since it is bilaterally symmetric and has almost no viewing angle dependency, it is presumed that two liquid crystal layers are laminated in a tilted orientation antiparallel as shown in FIG.

<Antireflection performance evaluation of organic EL display>
The optical film produced in Example 3 was prepared so that the tilt direction 8 of the commercially available polarizing plate 4 (SRW062 manufactured by Sumitomo Chemical Co., Ltd.), the absorption axis 5 of the polarizing plate 4 and the liquid crystal layer 7 in the optical film 12 was 45 degrees. The circularly polarizing plate 13 was produced by laminating to each other via an acrylic adhesive. At the time of bonding, the optical film 12 was laminated so that the liquid crystal layer 7 side was in contact with the polarizing plate 4. FIG. 16 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 4 and the liquid crystal layer 7 of the optical film 12. The hybrid structure is the reverse of the case of Example 1, and the liquid crystal layer 7 in the optical film 12 is such that the surface on which the liquid crystal molecules lie is on the side of the polarizing plate 4 and the surface on which the liquid crystal molecules stand more is polarized. On the opposite side of the plate 4.
The obtained circularly polarizing plate 13 was attached to a transparent glass substrate of an organic EL element of a commercially available organic EL display in the same manner as in Example 1 via an acrylic pressure-sensitive adhesive, and the organic EL display device of the present invention was attached. Created. As a result, it was found that an organic EL display device that exhibits a significant effect of preventing reflection of external light and has excellent visibility as compared with the case where no circularly polarizing plate is provided.
In addition, FIG. 17 and Table 1 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident with the reflection viewing angle measuring device EZ-CONTRAST manufactured by ELDIM and the front reflectance.

Example 4
<Preparation of polymerizable liquid crystal compound (B)>
A twist was added to the first mixture (polymerizable liquid crystal compound (A)) mixed in a mass ratio of 2 parts by weight of the compound (21) prepared in Example 1 and 17.6 parts by weight of the rod-like liquid crystal compound (22). A mixed solution was prepared in the same manner as in Example 1 except that a fourth mixture (polymerizable liquid crystal compound (B)) in which 0.15 wt% of a polymerizable liquid crystal compound (PALIOCOLOR LC756 manufactured by BASF) was mixed as a dopant was used. Prepared.

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

<Antireflection performance evaluation of organic EL display>
The optical film produced in Example 4 is a commercially available polarizing plate 4 (SRW062 manufactured by Sumitomo Chemical Co., Ltd.), the absorption axis 5 of the polarizing plate 4 and the polarizing plate 4 side orientation direction 14 of the liquid crystal layer 7 in the optical film 16 is 5. The circularly polarizing plate 17 was produced by pasting together with an acrylic pressure-sensitive adhesive so as to obtain a suitable degree. In this case, the alignment direction 15 of the liquid crystal molecules on the side opposite to the polarizing plate 4 of the liquid crystal layer 7 in the optical film 16 is 60 degrees. At the time of bonding, the optical film 16 was laminated so that the liquid crystal layer 7 side was in contact with the polarizing plate 4. FIG. 18 shows a schematic diagram of a cross-sectional structure of the polarizing plate 4 and the liquid crystal layer of the optical film 16 in the laminated state. The hybrid structure is the reverse of the case of Example 1, the liquid crystal layer 7 in the optical film 16, the surface on which the liquid crystal molecules lie more is on the polarizing plate 4 side, and the surface on which the liquid crystal molecules stand more is the polarizing plate. 4 and opposite side.
The obtained circularly polarizing plate 17 was attached to a transparent glass substrate of an organic EL element of a commercially available organic EL display in the same manner as in Example 1 via an acrylic pressure-sensitive adhesive, and the organic EL display device of the present invention was attached. Created. As a result, it was found that an organic EL display device that exhibits a significant effect of preventing reflection of external light and has excellent visibility as compared with the case where no circularly polarizing plate is provided.
In addition, FIG. 19 and Table 1 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident with a reflection viewing angle measuring device EZ-CONTRAST manufactured by ELDIM and the front reflectance.

(Comparative Example 1)
<Production of liquid crystal film>
Among the liquid crystal film manufacturing methods described in Example 1, the drying conditions after coating were applied in the same manner except that the drying conditions were pressure: 1013 hPa, temperature: 72 ° C. for 2 minutes, and then rapidly cooled to room temperature. An optical film (liquid crystal film / adhesive layer / TAC film) was obtained.
When the wavelength dispersion characteristic of retardation (Δn · d) in the front direction of the optical film and the average tilt were measured by measuring the phase difference in the oblique direction, Δn · d at a wavelength of 550 nm was 138 nm, and the average tilt angle was 0 degree. It was found to be homogeneous orientation (so-called parallel orientation).
The wavelength dispersion characteristics of birefringence are Δn · d (500) / Δn · d (550) = 0.98, Δn · d (600) / Δn · d (550) = 1.01, This coincided with the graph of the optical film produced in Example 1 (FIG. 9).

<Antireflection performance evaluation of organic EL display>
For the optical film produced in Comparative Example 1, the commercially available polarizing plate 4 (SRW062 manufactured by Sumitomo Chemical Co., Ltd.), the absorption axis 5 of the polarizing plate 4 and the alignment direction 8 of the liquid crystal layer 7 in the optical film 18 are 45 degrees. A circularly polarizing plate 19 was prepared by pasting together with an acrylic adhesive. At the time of bonding, the layers were laminated so that the TAC 9 side was in contact with the polarizing plate 4. FIG. 20 shows a schematic diagram of a cross-sectional structure in the laminated state of the polarizing plate 4 and the liquid crystal layer 7 of the optical film 18.
The obtained circularly polarizing plate 19 was attached to a transparent glass substrate of an organic EL element of a commercially available organic EL display via an acrylic pressure-sensitive adhesive in the same manner as in Example 1 to prepare an organic EL display device. As a result, it was found that an organic EL display device that exhibits a significant effect of preventing reflection of external light and has excellent visibility as compared with the case where no circularly polarizing plate is provided.
Further, Table 1 and Table 1 show the results of measuring the viewing angle characteristics of the reflectance when external light is incident with the reflection viewing angle measuring device EZ-CONTRAST manufactured by ELDIM and the front reflectance. When comparing Example 1 and Comparative Example 1, it can be seen that Example 1 is superior in viewing angle characteristics of reflectance. Since the wavelength dispersion characteristics of birefringence are the same, this difference in characteristics is thought to be due to the difference in liquid crystal alignment between nematic hybrid alignment and homogeneous alignment, and nematic hybrid alignment is effective in improving the viewing angle of antireflection performance. Suggests that.
In addition, when compared with Example 2, Example 3, Example 4 and Comparative Example 1, all the three examples are excellent in viewing angle characteristics of reflectance, so the structure of nematic hybrid orientation is turned upside down. It can be seen that even when the twisted structure is added to the nematic hybrid alignment, or when two layers of hybrid alignment are provided, the viewing angle can be improved.

(Comparative Example 2)
A nematic hybrid alignment liquid crystal film having Δn · d at a wavelength of 550 nm of 138 nm and an average tilt angle of 34 degrees was prepared by the liquid crystal material and the manufacturing method described in Example 1 of JP-A-10-186356. FIG. 22 summarizes the birefringence wavelength dispersion characteristics of the liquid crystal film layer, and Table 1 summarizes the optical characteristics results. Δn · d (500) / Δn · d (550) = 1.05, Δn · d (580) / Δn · d (550) = 0.97, and “positive dispersion” characteristics in the visible light region It was confirmed to have
In the same manner as in Example 1, it was bonded to a polarizing plate and adhered to an organic EL display. When viewed from the front, it was strongly bluish, and the antireflection performance was found to be significantly inferior to that of Example 1. This is considered because the birefringence wavelength dispersion characteristic of the liquid crystal film having a nematic hybrid alignment structure is insufficient.
Moreover, the result of having measured the viewing angle characteristic of the reflectance at the time of incident external light with the reflective viewing angle measuring apparatus EZ-CONTRAST made from ELDIM is shown in FIG. Although the effect of improving the viewing angle characteristics by the hybrid structure was confirmed, the reflectance was deteriorated as a whole due to the inferior birefringence wavelength dispersion characteristics.
As described above, as an antireflection performance of an organic EL display, a liquid crystal film having a “negative dispersion” characteristic in which the birefringence Δn increases in the visible light region as the measurement wavelength is longer, and has a nematic hybrid structure. However, it was confirmed that there was a significant improvement effect in the front and diagonal directions.

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

1: rod-shaped molecule 2: discotic molecule 3: liquid crystal film 4: polarizing plate 5: absorption axis 6, 12, 16, 18 of polarizing plate: optical film 7: liquid crystal layer 8: tilt direction 9: TAC films 10, 11, 13, 17, 19: Circularly polarizing plate 14: Liquid crystal alignment direction (polarizing plate side)
15: Liquid crystal alignment direction (TAC film side)

Claims (11)

  The retardation plate has a “negative dispersion” characteristic in which the birefringence Δn increases in the visible light region as the measurement wavelength becomes longer, and the retardation plate is made of a liquid crystal film in which a nematic hybrid alignment structure is fixed. A retardation film characterized by the following.   A retardation plate having a “negative dispersion” characteristic in which the birefringence Δn increases in the visible light region as the measurement wavelength becomes longer, and the retardation plate is made of a liquid crystal film in which a twisted nematic hybrid alignment structure is fixed. A retardation film characterized by that.   The retardation plate according to claim 1, wherein the liquid crystal film is a liquid crystal film in which a polymerizable liquid crystal compound is nematic hybrid aligned in a liquid crystal state and the alignment is fixed by a crosslinking reaction by light or heat.   The phase difference plate according to claim 2, wherein the liquid crystal film is a liquid crystal film in which a polymerizable liquid crystal compound is twisted nematic hybrid aligned in a liquid crystal state and the alignment is fixed by a crosslinking reaction by light or heat. . The retardation plate according to any one of claims 1 to 4, wherein a retardation ratio in a normal direction of the retardation plate at a specific wavelength satisfies the following formulas (1) and (2).
0.80 <Δn · d (500) / Δn · d (550) <1.00 (1)
1.00 <Δn · d (600) / Δn · d (550) <1.15 (2)
(Here, retardation is represented by the product of birefringence Δn and the film thickness d of the retardation plate, and Δn · d (500), Δn · d (550), and Δn · d (600) are respectively wavelengths. Retardation of retardation plate at 500 nm, 550 nm, and 600 nm.)   The retardation plate according to claim 1, wherein an average tilt angle of liquid crystal molecules of the liquid crystal film is 10 ° to 45 °.   The phase difference plate according to claim 1, wherein a twist angle in a film plane of liquid crystal molecules of the liquid crystal film is 0 ° to 90 °.   An elliptically polarizing plate comprising the retardation plate according to claim 1 and a polarizing plate bonded together.   The image display apparatus which has arrange | positioned the elliptically polarizing plate of Claim 8.   The liquid crystal display device which has arrange | positioned the elliptically polarizing plate of Claim 8. The organic electroluminescent display apparatus which has arrange | positioned the elliptically polarizing plate of Claim 8.

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