JP2006215221A - Polarizing element, liquid crystal panel, liquid crystal television, liquid crystal display device, and method for manufacturing polarizing element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing element that can increase a contrast ratio in an oblique direction of a liquid crystal display apparatus. <P>SOLUTION: The polarizing element comprises a polarizer, a positive A plate satisfying following expression (1), and a positive C plate satisfying following expression (2), in this order, wherein the positive A plate contains an optical retardation film comprising a solidified layer or cured layer of a liquid crystal composition aligned in a homogeneous arrangement, and the lagging axis of the positive A plate is substantially orthogonal to the absorption axis of the polarizer. The expressions are: 70 nm≤Re[590]≤200 nm...(1) and -200 nm≤Rth[590]≤-30 nm...(2), wherein Re[590] and Rth[590] represent phase difference values in the plane direction and in the thickness direction, respectively, measured at 23°C with light of 590 nm wavelength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizing element including a polarizer, a positive A plate, and a positive C plate. The present invention also relates to a liquid crystal panel, a liquid crystal television, and a liquid crystal display device including the polarizing element.

Various liquid crystal display devices, such as a liquid crystal display device having a conventional in-plane switching (IPS) mode liquid crystal cell, have an angle of 45 degrees (azimuth angle of 45 degrees, 135 degrees, 225 degrees, When the screen is viewed from an oblique direction at 315 degrees, there is a problem that the contrast ratio decreases, and a phenomenon (also referred to as color shift) that varies depending on the viewing angle of the display color increases. Therefore, a method for improving color shift by disposing a plurality of retardation films on one side of a liquid crystal cell is disclosed (for example, see Patent Document 1). However, with such a technique, although the color shift is improved, the contrast ratio in the oblique direction is not sufficiently improved.
JP 11-133408 A

  The present invention has been made to solve such problems, and an object of the present invention is to provide a polarizing element capable of increasing the contrast ratio in an oblique direction of a liquid crystal display device.

  As a result of intensive studies to solve the above problems, the present inventors have conventionally arranged a polarizing element in which a plurality of optical elements having a specific retardation value are stacked on a polarizer on at least one side of a liquid crystal cell. The present inventors have found that it is possible to provide a liquid crystal display device having an increased contrast ratio in an oblique direction as compared with those using the polarizing element.

The polarizing element of the present invention includes a polarizer, a positive A plate satisfying the following formula (1), and a positive C plate satisfying the following formula (2) in this order, and the positive A plate is oriented in a homogeneous array. A retardation film comprising a solidified layer or a cured layer of the liquid crystalline composition, wherein the slow axis of the positive A plate is substantially perpendicular to the absorption axis of the polarizer:
70 nm ≦ Re [590] ≦ 200 nm (1)
−200 nm ≦ Rth [590] ≦ −30 nm (2)
[However, Re [590] and Rth [590] are an in-plane retardation value and a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C., respectively. ].

  In a preferred embodiment, the refractive index (ne) of extraordinary light and ordinary light of a retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition aligned in the above homogeneous alignment, measured at 23 ° C. with light having a wavelength of 589 nm. The difference (ne−no) from the refractive index (no) is 0.04 to 0.20.

  In a preferred embodiment, the positive C plate includes a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition oriented in a homeotropic alignment.

  In preferable embodiment, the whole thickness of the said polarizing element is 20 micrometers-60 micrometers.

  According to another aspect of the present invention, a liquid crystal panel is provided. The liquid crystal panel includes the polarizing element and a liquid crystal cell.

  In a preferred embodiment, the polarizing element is arranged on the viewing side of the liquid crystal cell.

  In a preferred embodiment, the driving mode of the liquid crystal cell is an IPS mode, a VA mode, or an OCB mode.

  According to another aspect of the present invention, a liquid crystal television is provided. The liquid crystal television includes the liquid crystal panel.

  According to another aspect of the present invention, a liquid crystal display device is provided. The liquid crystal display device includes the liquid crystal panel.

  According to the present invention, by producing a polarizing element having specific constituent members (typically, retardation films) combined in a specific positional relationship, the advantages of the respective constituent members can be exhibited synergistically. The As a result, according to a liquid crystal panel using such a polarizing element (as a result, a liquid crystal display device), a contrast ratio in an oblique direction that is markedly superior to that of a conventional liquid crystal panel is realized. Further, as a positive A plate, by using a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement, the polarizing element is made thinner than the conventional one, and as a result, The liquid crystal panel and the liquid crystal display device can be thinned. Furthermore, when a liquid crystal compound having a birefringence in a specific range is used for the liquid crystalline composition, a retardation film having small in-plane retardation value variation can be obtained.

<< A. Overview of polarizing element >>
FIG. 1 is a schematic cross-sectional view of a polarizing element according to a preferred embodiment of the present invention. FIG. 2 is a schematic perspective view of the polarizing element. It should be noted that the ratio of the thicknesses of the constituent members in FIGS. 1 and 2 is shown differently from the actual one for ease of viewing. As shown in FIGS. 1 and 2, the polarizing element 10 includes a polarizer 11, a positive A plate 12, and a positive C plate 13 in this order. The positive A plate 12 includes a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement, and the slow axis of the positive A plate 12 is substantially the same as the absorption axis of the polarizer 11. Is orthogonal. Practically, any appropriate protective layer (typically a polymer film) can be disposed outside the polarizer 11 (the side where the positive A plate 12 is not disposed). In addition, an adhesive layer or a pressure-sensitive adhesive layer for adhering to the liquid crystal cell can be disposed outside the positive C plate 13 (side where the positive A plate 12 is not disposed). Details of the polarizer, the positive A plate, and the positive C plate will be described later in the B, C, and D terms, respectively.

  In another embodiment of the present invention, other constituent members may be disposed between the constituent members shown in FIG. Examples of other constituent members include, but are not limited to, an adhesive layer or an adhesive layer for attaching each constituent member, an isotropic film, and the like.

In the present invention, the positive A plate satisfies the following formula (1), and the positive C plate satisfies the following formula (2). By arranging such specific optical elements in at least one side of the polarizer in a specific order, extremely good optical compensation is performed, and as a result, the contrast ratio in the front and diagonal directions is increased and the diagonal directions are increased. A polarizing element capable of realizing a liquid crystal display device with a small color shift amount can be obtained.
70 nm ≦ Re [590] ≦ 200 nm (1)
−200 nm ≦ Rth [590] ≦ −30 nm (2)
[However, Re [590] and Rth [590] are an in-plane retardation value and a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C., respectively. ]

  The total thickness of the polarizing element is preferably 20 μm to 60 μm, more preferably 25 μm to 55 μm, and particularly preferably 30 μm to 50 μm. If it is said range, a very thin liquid crystal panel (as a result, a liquid crystal display device) can be obtained.

<< B. Polarizer
In this specification, a polarizer refers to a film that can be converted from natural light or polarized light into arbitrary polarized light. Any appropriate polarizer may be adopted as the polarizer used in the present invention, but a polarizer that converts natural light or polarized light into linearly polarized light is preferably used.

  Any appropriate thickness can be adopted as the thickness of the polarizer. The thickness of the polarizer is typically 5 μm to 50 μm, preferably 10 μm to 40 μm, and more preferably 20 μm to 30 μm. If it is said range, it is excellent in an optical characteristic and mechanical strength.

  The transmittance of the polarizer measured at 23 ° C. at a wavelength of 440 nm (also referred to as single transmittance) is preferably 41% or more, more preferably 43% or more. Note that the theoretical upper limit of the single transmittance is 50%. The degree of polarization is preferably 99.8% to 100%, and more preferably 99.9% to 100%. If it is said range, when it uses for a liquid crystal display device, the contrast ratio of a front direction can be made still higher.

The single transmittance and the degree of polarization can be measured using a spectrophotometer [product name “DOT-3” manufactured by Murakami Color Research Laboratory Co., Ltd.]. As a specific method for measuring the degree of polarization, the parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the polarizer are measured, and the formula: degree of polarization (%) = {(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100. The parallel transmittance (H ₀ ) is a value of the transmittance of a parallel laminated polarizer prepared by superposing two identical polarizers so that their absorption axes are parallel to each other. The orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal laminated polarizer produced by superposing two identical polarizers so that their absorption axes are orthogonal to each other. Note that these transmittances are Y values obtained by correcting the visibility using the 2-degree field of view (C light source) of JlSZ8701-1982.

  Examples of the polarizer used in the present invention include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, ethylene / vinyl acetate copolymer partially saponified films, iodine and dichroism. Examples include uniaxially stretched films by adsorbing dichroic substances such as dyes, and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film and uniaxially stretching is particularly preferable because of its high degree of polarization.

  Further, as the polarizer used in the present invention, in addition to the above-described polarizer, for example, a stretched film of a polymer film containing a dichroic substance such as iodine or a dichroic dye, a dichroic substance and liquid crystal A guest-host type O-type polarizer (US Pat. No. 5,523,863) in which a liquid crystalline composition containing a compound is aligned in a certain direction, and an E-type polarizer in which lyotropic liquid crystal is aligned in a certain direction ( US Pat. No. 6,049,428) can also be used.

  Referring to FIG. 2, the polarizer 11 is disposed on one side of the positive A plate 12. As a method of arranging the polarizer 11, any appropriate method can be adopted depending on the purpose. Preferably, the polarizer 11 is provided with an adhesive layer or a pressure-sensitive adhesive layer (not shown) on the surface facing the liquid crystal cell, and is adhered to the surface of the positive A plate 12. By filling the space between the optical elements with the adhesive layer or the pressure-sensitive adhesive layer in this manner, the optical axis of each optical element can be prevented from shifting when incorporated in a liquid crystal display device, Can be prevented from being rubbed and damaged. Further, the interface reflection between the layers of each optical element can be reduced, and the contrast can be increased when used in a liquid crystal display device.

  The thickness of the adhesive layer or the pressure-sensitive adhesive can be appropriately determined according to the purpose of use and adhesive force, and the preferable range of the thickness of the adhesive is generally 0.1 μm to 50 μm, preferably 0.00. 1 μm to 20 μm, particularly preferably 0.1 μm to 10 μm. A suitable thickness range of the pressure-sensitive adhesive is generally 1 μm to 100 μm, preferably 5 μm to 80 μm, and particularly preferably 10 μm to 50 μm.

  Any appropriate adhesive or pressure-sensitive adhesive can be adopted as the adhesive or pressure-sensitive adhesive forming the adhesive layer or pressure-sensitive adhesive layer depending on the purpose. As the adhesive, an aqueous adhesive is preferably used in terms of excellent adhesiveness, workability, and environmental performance. Particularly preferred is an aqueous adhesive mainly composed of a polyvinyl alcohol resin. As a specific example, an adhesive mainly having a modified polyvinyl alcohol having an acetoacetyl group [manufactured by Nippon Synthetic Chemical Co., Ltd., trade name “Gosefimer Z200”] can be mentioned. As the pressure-sensitive adhesive, acrylic polymer is used as the base polymer in terms of excellent optical transparency, moderate wettability, cohesiveness and adhesive properties, and excellent weather resistance and heat resistance. An acrylic adhesive is preferably used. As a specific example, a double-sided optical tape [trade name “SK-2057” manufactured by Soken Chemical Co., Ltd.] having an acrylic pressure-sensitive adhesive as a pressure-sensitive adhesive layer can be mentioned.

<< C. Positive A plate
In this specification, the positive A plate means that the in-plane main refractive index is nx (refractive index in the slow axis direction), ny (refractive index in the fast axis direction), and the refractive index in the thickness direction is nz. An optical element exhibiting positive uniaxiality in which the refractive index distribution satisfies nx> ny = nz (ideally, an optical element exhibiting positive uniaxiality has an optical axis in one direction in the plane) Say. In this specification, ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same. Here, “when ny and nz are substantially the same” means, for example, an in-plane retardation value (Re [590]) and a thickness direction retardation value (Rth [590]). The absolute value of the difference is included: | Rth [590] −Re [590] | is 10 nm or less.

<< C-1. Optical properties of positive A plate >>
In this specification, Re [590] refers to an in-plane retardation value measured with light having a wavelength of 590 nm at 23 ° C. Re [590] is when the in-plane slow axis direction and fast axis direction refractive indexes at a wavelength of 590 nm are nx and ny, respectively, and d (nm) is the thickness of the optical element (or retardation film). The equation: Re [590] = (nx−ny) × d. The slow axis means the direction in which the in-plane refractive index is maximum.

  Re [590] of the positive A plate used in the present invention is 70 nm to 200 nm, preferably 100 nm to 180 nm, more preferably 120 nm to 160 nm, and particularly preferably 130 nm to 150 nm. By setting Re [590] in the above range, the contrast ratio in the oblique direction of the liquid crystal display device can be increased.

  In this specification, Rth [590] refers to a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C. Rth [590] represents the refractive index in the slow axis direction and the thickness direction of the optical element (or film) at a wavelength of 590 nm as nx and nz, respectively, and d (nm) as the thickness of the optical element (or retardation film). Then, it can be obtained by the formula: Rth [590] = (nx−nz) × d. The slow axis refers to the direction in which the in-plane refractive index is maximum.

  The absolute value of the difference between Re [590] and Rth [590] of the positive A plate used in the present invention: | Rth [590] −Re [590] | is preferably 0 nm to 5 nm, more preferably 0 nm. ~ 2 nm. By setting it as the above range, the contrast ratio in the oblique direction of the liquid crystal display device can be increased, and the color shift amount in the oblique direction can be reduced.

Re [590] and Rth [590] can also be obtained by using a trade name “KOBRA21-ADH” manufactured by Oji Scientific Instruments. In-plane retardation value (Re) at a wavelength of 590 nm at 23 ° C., retardation value (R40) measured by tilting the slow axis as an inclination axis by 40 degrees, retardation film thickness (d), and retardation film Using the average refractive index (n0), nx, ny and nz can be obtained by computer numerical calculation from the following formulas (i) to (iv), and then Rth can be calculated by formula (iv). Here, φ and ny ′ are represented by the following equations (v) and (vi), respectively.
Re = (nx−ny) × d (i)
R40 = (nx−ny ′) × d / cos (φ) (ii)
(Nx + ny + nz) / 3 = n0 (iii)
Rth = (nx−nz) × d (iv)
φ = sin ⁻¹ [sin (40 °) / n0] (v)
ny ′ = ny × nz [ny ² × sin ² (φ) + nz ² × cos ² (φ)] ^1/2 (vi)

  The transmittance of the positive A plate measured with light having a wavelength of 590 nm at 23 ° C. is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more.

<< C-2. Positioning means for positive A plate >>
Referring to FIG. 2, as a method of arranging the positive A plate 12 between the polarizer 11 and the positive C plate 13, an appropriate method can be appropriately adopted according to the purpose. Preferably, the positive A plate 12 is provided with an adhesive layer or a pressure-sensitive adhesive layer (not shown) on both sides thereof, and is adhered to the surfaces of the polarizer 11 and the positive C plate 13. By filling the gaps between the optical elements with the adhesive layer or the pressure-sensitive adhesive layer in this way, the optical axes of the optical elements can be prevented from shifting when they are incorporated into a liquid crystal display device, Can be prevented from being rubbed and damaged. Further, the interface reflection between the layers of each optical element can be reduced, and the contrast can be increased when used in a liquid crystal display device.

  The thickness of the adhesive layer or the pressure-sensitive adhesive can be appropriately determined according to the purpose of use and adhesive force, and the preferable range of the thickness of the adhesive is generally 0.1 μm to 50 μm, preferably 0.00. 1 μm to 20 μm, particularly preferably 0.1 μm to 10 μm. A suitable thickness range of the pressure-sensitive adhesive is generally 1 μm to 100 μm, preferably 5 μm to 80 μm, and particularly preferably 10 μm to 50 μm.

  Any appropriate adhesive or pressure-sensitive adhesive can be adopted as the adhesive or pressure-sensitive adhesive forming the adhesive layer or pressure-sensitive adhesive layer depending on the purpose. Examples of the adhesive include thermoplastic adhesives, hot melt adhesives, rubber adhesives, thermosetting adhesives, monomer reaction adhesives, inorganic adhesives, natural product adhesives, and the like. Examples of the pressure-sensitive adhesive include solvent-based pressure-sensitive adhesives, non-aqueous emulsion-type pressure-sensitive adhesives, water-based pressure-sensitive adhesives, hot-melt pressure-sensitive adhesives, liquid-curing pressure-sensitive adhesives, curable pressure-sensitive adhesives, and pressure-sensitive adhesives by a calendar method. . Particularly preferred is a solvent-based adhesive having an acrylic polymer as a base polymer in terms of excellent optical transparency, moderate wettability, cohesiveness and adhesive properties, and excellent weather resistance and heat resistance. An agent (also referred to as an acrylic pressure-sensitive adhesive) is preferably used. As a specific example, a double-sided optical tape [trade name “SK-2057” manufactured by Soken Chemical Co., Ltd.] having an acrylic pressure-sensitive adhesive as a pressure-sensitive adhesive layer can be mentioned.

  As described above, the positive A plate 12 is arranged so that its slow axis is substantially perpendicular to the absorption axis of the polarizer 11. In this specification, “substantially orthogonal” includes a case where the angle formed by the absorption axis of the polarizer 11 and the slow axis of the positive A plate 12 is 90 ° ± 2.0 °. The angle is preferably 90 ° ± 1.0 °, more preferably 90 ° ± 0.5 °. As the degree of deviation from these angular ranges increases, the contrast tends to decrease when used in a liquid crystal display device.

<< C-3. Composition of positive A plate >>
The configuration (laminated structure) of the positive A plate includes a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement, and satisfies the optical characteristics described in the above section C-1. If there is no particular limitation. Specifically, the positive A plate may be a single retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement, and the retardation film and any other retardation film. The laminated body comprised by 2 or more sheets containing these may be sufficient. Preferably, the positive A plate is a retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition aligned in a single homogeneous arrangement. This is because the shift and unevenness of the retardation value due to the contraction stress of the polarizer and the heat of the backlight can be reduced, and the liquid crystal panel can be made thin. When the positive A plate is a laminate, an adhesive layer or a pressure-sensitive adhesive layer may be included. When the laminate includes two or more retardation films, these retardation films may be the same or different. The details of the retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement will be described later in Section C-4.

  Re [590] of the retardation film used for the positive A plate can be appropriately selected depending on the number of the retardation films used. For example, when the positive A plate is composed of a single retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement, Re [590] of the retardation film represents the positive A plate. It is preferable to be equal to Re [590]. Therefore, it is preferable that the retardation value of the adhesive layer or the pressure-sensitive adhesive layer used when the positive A plate is laminated on the polarizer or the positive C plate is as small as possible. For example, when the positive A plate is a laminate including two or more retardation films, the sum of Re [590] of each retardation film is equal to Re [590] of the positive A plate. It is preferable to design as follows. Specifically, when two positive retardation films are laminated so that their slow axes are parallel to each other to produce a positive A plate with Re [590] of 140 nm, Re [590] can be set to 70 nm. Here, for the sake of simplicity, only the case where the number of retardation films is two or less is shown, but it goes without saying that the present invention can also be applied to a laminate including three or more retardation films.

  The total thickness of the positive A plate is preferably 1 μm to 20 μm, more preferably 1.2 μm to 10 μm, and particularly preferably 1.5 μm to 5 μm. By setting the thickness of the optical element in the above range, it is possible to obtain an optical element that is thin (as a result, contributes to thinning of the liquid crystal display device) and has small in-plane retardation value variation.

<< C-4. Retardation film used for positive A plate >>
In the present invention, the positive A plate includes a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition oriented in a homogeneous arrangement. In the present specification, “homogeneous alignment” refers to a state in which the liquid crystal compounds contained in the liquid crystalline composition are aligned in parallel and in the same direction with respect to the film plane. Further, the “solidified layer” refers to a solidified state in which a liquid crystalline composition in a softened, molten or solution state is cooled. The “cured layer” is a layer in which a part or all of the liquid crystalline composition is cross-linked by heat, catalyst, light and / or radiation to be in a stable state of infusible or hardly soluble. Say. The “cured layer” includes a cured layer formed through a solidified layer of a liquid crystal composition.

  The “liquid crystalline composition” refers to a liquid crystal phase exhibiting liquid crystallinity. Examples of the liquid crystal phase include a nematic liquid crystal phase, a smectic liquid crystal phase, a cholesteric liquid crystal phase, and a columnar liquid crystal phase. The liquid crystalline composition used in the present invention preferably exhibits a nematic liquid crystal phase. This is because a highly transparent retardation film can be obtained.

  The liquid crystalline composition is not particularly limited as long as it contains a liquid crystal compound and exhibits liquid crystallinity. The content of the liquid crystal compound in the liquid crystal composition is preferably 40 to 100 (weight ratio), more preferably 50 to 99 (weight ratio) with respect to the total solid content 100 of the liquid crystal composition. And particularly preferably 70 to 98 (weight ratio). In the liquid crystalline composition, various additives such as a solvent, a leveling agent, a polymerization initiator, an alignment agent, a heat stabilizer, a lubricant, a lubricant, a plasticizer, and an antistatic agent are used within the range not impairing the object of the present invention. May be included.

  In the present specification, the “liquid crystal compound” refers to a molecule having a mesogenic group in a molecular structure and forming a liquid crystal phase by a temperature change such as heating or cooling or by the action of a certain amount of solvent. The “mesogen group” means a structural portion necessary for forming a liquid crystal phase, and usually contains a cyclic unit. Specific examples of the mesogenic group include, for example, a biphenyl group, a phenylbenzoate group, a phenylcyclohexane group, an azoxybenzene group, an azomethine group, an azobenzene group, a phenylpyrimidine group, a diphenylacetylene group, a diphenylbenzoate group, a bicyclohexane group, and a cyclohexyl group. Examples thereof include a benzene group and a terphenyl group. In addition, the terminal of these cyclic units may have substituents, such as a cyano group, an alkyl group, an alkoxy group, a halogen group, for example. Especially, as a mesogenic group which consists of a cyclic unit etc., what has a biphenyl group and a phenylbenzoate group is used preferably.

  The liquid crystal compound may be either a temperature transition type (thermotropic) liquid crystal in which a liquid crystal phase develops due to a temperature change, or a concentration transition type (lyotropic) liquid crystal in which a liquid crystal phase develops depending on the concentration of a solute in a solution state. Note that the above-described temperature transition type liquid crystal has a phase transition from a crystalline phase (or glass state) to a liquid crystal phase, a reversible tautomatic (enantotropic) phase transition liquid crystal, or a single change in which a liquid crystal phase appears only in a temperature lowering process ( Monotropic) phase transition liquid crystals. Preferably, the liquid crystal compound is a temperature transition type (thermotropic) liquid crystal. It is because it is excellent in productivity, workability, and quality of film forming.

  The liquid crystal compound may be a high molecular substance (polymer liquid crystal) having a mesogenic group in the main chain and / or side chain, or a low molecular substance (low molecular liquid crystal) having a mesogenic group in a part of the molecular structure. There may be. Polymer liquid crystal has features such as high film forming productivity and excellent heat resistance, mechanical strength, chemical resistance, etc., because the molecular alignment state can be fixed just by cooling from the liquid crystal state. . Since the low molecular liquid crystal is excellent in orientation, it has a feature that a highly transparent film can be easily obtained.

  The liquid crystal compound is preferably a low molecular substance (low molecular liquid crystal) each having at least one mesogenic group and a polymerizable functional group in a part of the molecular structure. More preferably, it is a low molecular liquid crystal having one or more mesogenic groups and two or more polymerizable functional groups in a part of the molecular structure. This is because a retardation film having excellent orientation and extremely high optical uniformity and transparency can be obtained. Moreover, if the polymerizable functional group is crosslinked by a polymerization reaction, the mechanical strength of the retardation film is increased, and a retardation film having excellent durability and dimensional stability can be obtained. Specific examples of the low-molecular liquid crystal having one or more mesogenic groups and two or more polymerizable functional groups in a part of the molecular structure include a product name “Paliocolor LC242” manufactured by BASF and a product name “manufactured by HUNTSMAN” CB483 "etc. are mentioned.

  Any appropriate functional group can be selected as the polymerizable functional group. For example, acryloyl group, methacryloyl group, epoxy group, vinyl ether group and the like can be mentioned. Of these, an acryloyl group and a methacryloyl group are preferably used. This is because, in addition to excellent reactivity, a highly transparent retardation film can be obtained.

The refractive index (ne) of extraordinary light measured at a wavelength of 589 nm at 23 ° C. and the refractive index (no) of ordinary light of a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement. The difference: Δn _LC = ne−no (also referred to as birefringence) is preferably 0.04 to 0.20. More preferably, it is 0.05-0.15, Most preferably, it is 0.05-0.09. If it is said range, the thin phase difference film with a small dispersion | variation in retardation value within a surface can be obtained. The birefringence is measured using an Abbe refractometer, Shoichi Matsumoto, “Basics and Applications of Liquid Crystals” p. 45.

  The thickness of the retardation film composed of a solidified layer or a cured layer of the liquid crystalline composition aligned in the homogeneous arrangement is preferably 1 μm to 10 μm, more preferably 1.2 μm to 5 μm, and particularly preferably 1 .5 μm to 3 μm. The said optical element can contribute to thickness reduction of a liquid crystal display device by setting it as the range of said thickness.

<< C-5. Method for producing retardation film used for positive A plate >>
Preferably, as a method for producing a retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement, (Step A-1) horizontal alignment treatment is performed on the surface of a substrate (also referred to as a temporary support). (Step A-2) A step of applying a solution or dispersion of a liquid crystalline composition to the surface of the substrate subjected to the horizontal alignment treatment, and aligning the liquid crystalline composition in a homogeneous alignment And (Step A-3) a step of drying and solidifying the liquid crystalline composition. More preferably, in the production method of the present invention, after (Step A-1) to (Step A-3), (Step A-4) a step of irradiating ultraviolet rays to cure the liquid crystalline composition, including. In general, the substrate is peeled off before the retardation film is put into practical use.

  3-5 is a schematic diagram explaining the outline | summary of the manufacturing method of a positive A plate as an example of preferable embodiment. FIG. 3 is a schematic diagram for explaining the outline of the step of performing the horizontal alignment treatment on the surface of the substrate (1), and illustrates the case where a solution coating method and a photo-alignment method described later are employed. In this step, the base material 102 is supplied from the feeding unit 101, conveyed by the guide roll 103, and the solution or dispersion liquid of the alignment agent is applied in the coater unit 104. The base material coated with the alignment agent is sent to the drying means 105 and the solvent is evaporated to form an alignment film. Next, the substrate on which the alignment film is formed is sent to the ultraviolet irradiation unit 109, and the surface of the alignment film is irradiated with polarized ultraviolet light. The ultraviolet irradiation unit 109 typically includes an ultraviolet lamp 107, a polarizing filter 108, and a temperature control unit 106. The polarizer 108 is used to control the alignment method of the liquid crystalline composition. Next, the substrate that has been subjected to the horizontal alignment treatment is wound up by the winding unit 110 and is subjected to a coating / drying step of the liquid crystalline composition.

  FIG. 4 shows the step (step A-2) of applying a solution or dispersion of a liquid crystalline composition to the surface of the substrate that has been subjected to the horizontal alignment treatment, and orienting the liquid crystalline composition in a homogeneous array. The outline of the step, the step (step A-3) of drying and solidifying the liquid crystalline composition, and the step of curing the liquid crystalline composition by irradiating with the ultraviolet ray (step A-4). It is a schematic diagram to do. In these steps, the base material 202 that has been subjected to the horizontal alignment treatment is supplied from the feeding unit 201 and conveyed by the guide roll 203, and the liquid crystal composition solution or dispersion is applied in the coater unit 204. . The substrate coated with the liquid crystalline composition is sent to the drying means 205, where the solvent is evaporated to form a solidified layer of the liquid crystalline composition oriented in a homogeneous arrangement. Next, the substrate on which the solidified layer of the liquid crystal composition aligned in the homogeneous arrangement was formed was sent to the ultraviolet irradiation unit 208, and the surface of the solidified layer was irradiated with ultraviolet light to be aligned in the homogeneous arrangement. A cured layer of the liquid crystal composition is formed. The ultraviolet irradiation unit 208 typically includes an ultraviolet lamp 207 and a temperature control means 206. Next, the substrate coated with the liquid crystalline composition is wound up by the winding unit 209 and used for the manufacturing process of the polarizing element. In addition, even when the liquid crystalline composition includes a polymer liquid crystal, even when the solidified layer is used, when the retardation film having a practically sufficient mechanical strength can be obtained, the ultraviolet irradiation step can be omitted. .

<< C-5-1. Horizontal alignment process >>
(Step A-1) In the step of applying a horizontal alignment treatment to the surface of the substrate, the horizontal alignment treatment is used to align the liquid crystalline composition in a homogeneous alignment. As the horizontal alignment treatment, an appropriate method can be appropriately selected according to the purpose. Specific examples include (A) a method of forming an alignment film (also referred to as an alignment layer) by adsorbing an alignment agent on the surface of the substrate, and (B) a surface of the substrate (or alignment film) in shape. The method of changing is mentioned. Preferably, the horizontal alignment treatment is a method in which an alignment agent is adsorbed on the surface of the substrate to form the alignment film, and then the surface of the alignment film is changed in shape. This is because a retardation film having extremely few alignment defects (disclination) of the liquid crystal composition can be produced.

  Examples of the method for adsorbing the alignment agent on the surface of the substrate include a solution coating method, a plasma polymerization method, and a sputtering method. Among these methods, the solution coating method is preferably used as the present invention. It is because it is excellent in continuous productivity, workability, and economical efficiency, and the liquid crystalline composition can be uniformly aligned. In the present specification, the “solution coating method” refers to a method of forming an alignment film by applying a solution or dispersion of an alignment agent on the surface of a substrate and drying it.

  Any appropriate alignment agent can be selected as the alignment agent used in the horizontal alignment treatment. Specific examples include carbon, polyoxyethylene, versaamide 125, polyvinyl alcohol, polyimide, dibasic carboxylic acid chromium complex, organic silane, acetylene, dibasic fatty acid, crown ether and the like.

  As a method for preparing the alignment agent solution or dispersion, a commercially available alignment agent solution or dispersion may be used, or a solvent may be further added to the commercially available alignment agent solution or dispersion. . Further, the solid content of the alignment agent may be dissolved in various solvents and used, or the alignment agent, various additives, and a solvent may be mixed and dissolved.

  The total solid content concentration of the solution of the aligning agent varies depending on solubility, coating viscosity, wettability on the substrate, thickness after coating, etc. -20 (weight ratio), more preferably 0.5 to 10 (weight ratio), particularly preferably 1 to 5 (weight ratio). If it is said range, a phase difference film with high surface uniformity can be obtained.

  Examples of a method for deforming the surface of the substrate (or alignment film) in shape include a rubbing method, a photo-alignment method, an oblique deposition method, an ion beam method, a plasma method, and a pulling coating method. Among these methods, the photo-alignment method is preferably used as the present invention. In this specification, the “photo-alignment method” refers to irradiating light on the surface of an alignment film (also referred to as a photo-alignment film) containing a compound having at least one photoreactive functional group in the molecular structure, It refers to a method of uniformly aligning a liquid crystal compound by sterically changing a photoreactive functional group. In the present specification, “photochemical reaction” refers to a reaction that sterically changes a photoreactive functional group.

  Since the photo-alignment method is a process that generates very little static electricity, dust, dust, etc., a retardation film with excellent quality can be produced. Furthermore, the direction in which the slow axis of the retardation film is generated can be controlled in an in-plane direction depending on the direction and direction of light irradiation. For example, a retardation film having a slow axis in a direction perpendicular to the longitudinal direction and used as a positive A plate can be produced as a roll, and the roll-like retardation film is absorbed in parallel with the longitudinal direction. Since the polarizing element of the present invention can be produced by continuously laminating a roll-shaped polarizer having an axis with a roll-to-roll, the productivity of the polarizing element can be greatly improved.

  FIG. 5 is a schematic perspective view of a typical ultraviolet irradiation unit (in the case where the alignment film is irradiated with polarized light) used in the photo-alignment method. The ultraviolet irradiation unit 300 includes a rod-shaped dielectric excimer discharge lamp 301 in which a mixed gas of xenon and chlorine is sealed in a discharge vessel, a condensing mirror 302 having a circular or elliptical cross section, and a polarizing filter 303 (typically , Wire grid polarizer) and temperature control means (not shown). The polarizing filter 303 is arranged so that its longitudinal direction coincides with the longitudinal direction of the lamp 301. In another embodiment, the polarizing filter 303 may be omitted when non-polarized light is irradiated on the alignment film depending on the alignment agent or the type of photochemical reaction.

  As the aligning agent used for the photo-alignment film, an appropriate one can be appropriately selected as long as it contains a compound having at least one photoreactive functional group in the molecular structure. For example, those containing a compound having a photoreactive functional group that causes a photochemical reaction such as a photoisomerization reaction, a photo-opening / closing ring reaction, a photo-dimerization reaction, a photolysis reaction, and a photo-fleece transfer reaction are used. Among these, a compound having a photoreactive functional group that causes a photoisomerization reaction and / or a photodimerization reaction is preferable. This is because a retardation film having high surface uniformity can be obtained.

  Specific examples of the photoreactive functional group that causes a photoisomerization reaction include azobenzene group, stilbene group, α-hydrazono-β-ketoester group, cinnamate group, benzylidenephthalimidine group, retinoic acid and the like. Specific examples of the photoreactive functional group that causes a photodimerization reaction include a cinnamate group, a benzylidenephthalimidine group, a chalcone group, a coumarin group, a styrylpyridine group, and an anthracene group.

  Specific examples of the compound having a photoreactive functional group include a product name “Staralign series (2100, 2110)” manufactured by HUNTSMAN, Chem. Mater. 2001, 13, p. 695, a compound having a coumarin group described in Table 1, JSR TECHNIC REVIEW No. 106 (1999) in FIG. 1, JSR TECHNIC REVIEW No. 107 (2000) and the compound having a chalcone group described in FIG.

  Particularly preferred as the aligning agent used in the photo-alignment film is an aligning agent containing a compound having at least one photoreactive functional group selected from a cinnamate group, a chalcone group and an azobenzene group. This is because the photochemical reaction efficiency is excellent and the liquid crystalline composition can be uniformly oriented. As a result, a retardation film having excellent optical uniformity and high transparency can be obtained. In particular, the 4-chalcone group has a characteristic that it has good reactivity with long-wavelength ultraviolet light that is unlikely to deteriorate due to a photolytic reaction, and is excellent in heat resistance.

  The method of irradiating the surface of the photo-alignment film with light depends on the type of photochemical reaction of the compound having a photoreactive functional group used in the photo-alignment film and the direction of the slow axis of the target retardation film. Thus, an appropriate method can be selected as appropriate. Examples of the light source used for light irradiation include an ultrahigh pressure mercury lamp, a dielectric excimer discharge lamp, a flash UV lamp, a high pressure mercury lamp, a low pressure mercury lamp, a deep UV lamp, a xenon lamp, a xenon flash lamp, and a metal halide lamp.

  The wavelength of the light source used for the light irradiation may be appropriately selected depending on the wavelength region in which the compound having a photoreactive functional group used for the photo-alignment film has optical absorption. Preferably, the wavelength of the light source is preferably 210 nm to 380 nm, more preferably 230 nm to 380 nm, and particularly preferably 250 nm to 380 nm. The wavelength of the light source is preferably used by cutting a region of 100 nm to 200 nm with a filter or the like in order to suppress the photodecomposition reaction of the photo-alignment film. If it is said range, a liquid crystalline composition can be uniformly orientated to a homogeneous arrangement | sequence.

Preferably the irradiation light amount of the light, the value measured at a wavelength of 310nm is a ^{5mJ / cm 2 ~500mJ / cm 2} , more preferably from ^{5mJ / cm 2 ~500mJ / cm 2} , particularly preferably 10 mJ / cm ^{2 to} 300 mJ / cm ² . If it is the irradiation light quantity of the said range, if it is said range, a liquid crystalline composition can be orientated uniformly in a homogeneous arrangement | sequence.

  The temperature in the irradiation apparatus during irradiation with light (also referred to as irradiation temperature) is preferably kept below the liquid crystal phase-isotropic phase transition temperature (Ti) of the liquid crystalline composition. More preferably, it is the range of Ti-5 degrees C or less, Most preferably, it is the range of Ti-10 degrees C or less. Specifically, the irradiation temperature is preferably 15 ° C to 90 ° C, more preferably 15 ° C to 60 ° C. If it is said temperature range, a highly uniform retardation film can be produced.

  The liquid crystal phase-isotropic phase transition temperature (Ti) is obtained by sandwiching the liquid crystalline composition used in the present invention between two glass slides, and a temperature controller (for example, product name “LK-600PM” manufactured by Japan Hightech Co., Ltd.). ) It is obtained by measuring the temperature when a dark field is obtained from a bright field when observing while raising the temperature with a polarizing microscope in which two polarizers are arranged in a crossed Nicol arrangement. be able to.

  Examples of the method for maintaining the irradiation temperature constant include, for example, an air circulation type constant temperature oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, a roll heated for temperature control, a heat pipe roll, An appropriate one can be appropriately selected from a heating method such as a metal belt and a temperature control method.

<< C-5-2. Method for applying liquid crystal composition solution or dispersion liquid >>
In the step of applying the solution or dispersion of the liquid crystalline composition to the surface of the substrate subjected to the above-mentioned (Step A-2) horizontal alignment treatment and aligning the liquid crystalline composition in a homogeneous alignment, An appropriate material can be selected as appropriate. Specific examples include glass substrates such as glass plates and quartz substrates, polymer substrates such as films and plastics substrates, metal substrates such as aluminum and iron, inorganic substrates such as ceramic substrates, and semiconductors such as silicon wafers. Examples include base materials. Preferably, the substrate is a polymer substrate. This is because the surface smoothness of the base material and the wettability of the liquid crystal composition are excellent, and continuous production with a roll is possible, and the productivity can be greatly improved.

  Examples of the material for forming the polymer substrate include thermosetting resins, ultraviolet curable resins, thermoplastic resins, thermoplastic elastomers, and biodegradable plastics. Of these, thermoplastic resins are preferably used. The thermoplastic resin may be an amorphous polymer or a crystalline polymer. Since the amorphous polymer is excellent in transparency, it has an advantage that the retardation film of the present invention can be used as it is for a liquid crystal panel or the like without peeling off from the substrate. On the other hand, since the crystalline polymer is excellent in rigidity, strength, and chemical resistance, it has an advantage that it is excellent in production stability when the retardation film of the present invention is produced. The polymer base material is preferably polyethylene terephthalate. This is because it is excellent in surface uniformity, strength, chemical resistance, production stability and the like. The polyethylene terephthalate is usually peeled off before a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition oriented in a homogeneous arrangement is put to practical use.

  As a method of preparing a liquid crystal composition solution or dispersion, a commercially available liquid crystal composition solution or dispersion may be used, and a solvent is further added to the commercially available liquid crystal composition solution or dispersion. May be used. Further, the solid content of the liquid crystalline composition may be used by dissolving it in various solvents, or an aligning agent, various additives, and a solvent may be mixed and dissolved.

  The total solid content concentration of the liquid crystal composition solution varies depending on the solubility, coating viscosity, wettability on the substrate, thickness after coating, etc. -100 (weight ratio), more preferably 30-80 (weight ratio), particularly preferably 40-60 (weight ratio). If it is said range, a phase difference film with high surface uniformity can be obtained.

  As the solvent, a liquid substance that uniformly dissolves the liquid crystalline composition to form a solution is preferably used. The solvent may be a nonpolar solvent such as benzene or hexane, or a polar solvent such as water or alcohol. The solvent may be an inorganic solvent such as water, alcohols, ketones, ethers, esters, aliphatic and aromatic hydrocarbons, halogenated hydrocarbons, amides, cellosolves. Organic solvents such as Preferably, it is at least one solvent selected from cyclopentanone, cyclohexanone, methyl isobutyl ketone, methyl ethyl ketone, toluene, ethyl acetate and tetrahydrofuran. These solvents are preferable because they do not cause erosion that has a practically adverse effect on the substrate and can sufficiently dissolve the above composition.

  As a method for applying the liquid crystal composition solution or dispersion, an appropriate coating method using a coater can be appropriately selected and used. Specific examples of the above coater include reverse roll coater, forward rotation roll coater, gravure coater, knife coater, rod coater, slot orifice coater, curtain coater, fountain coater, air doctor coater, kiss coater, dip coater, bead coater, blade coater, cast Examples include a coater, a spray coater, a spin coater, an extrusion coater, and a hot melt coater. Among these, as a coater, a reverse roll coater, a normal rotation roll coater, a gravure coater, a rod coater, a slot orifice coater, a curtain coater, a fountain coater, and a spin coater are preferable. If it is a coating method using the above-mentioned coater, it is possible to obtain a retardation film that is very thin and excellent in surface uniformity and optical uniformity.

<< C-5-3. Method for Drying Solution or Dispersion of Liquid Crystalline Composition >>
In the step (step A-3) of drying and solidifying the liquid crystalline composition aligned in a homogeneous arrangement, a method of drying the liquid crystalline composition (also referred to as drying means) is, for example, hot air or cold air Appropriately appropriate from heating method and temperature control method such as air circulation type constant temperature oven in which the air circulates, heater using microwave or far infrared ray, roll heated for temperature control, heat pipe roll or metal belt Can be selected.

  Although there is no restriction | limiting in particular as temperature (drying temperature) in the said drying means, It is preferable to carry out in the temperature range which shows the liquid crystal phase of the said liquid crystalline composition. Moreover, it is preferable that it is below the glass transition temperature (Tg) of a base material. A preferable range of the drying temperature is 50 ° C to 130 ° C. More preferably, it is 80 degreeC-120 degreeC. If it is said temperature range, a highly uniform retardation film can be produced.

  The time for drying treatment (drying time) is not particularly limited, but is, for example, 1 minute to 20 minutes, preferably 1 minute in order to obtain a retardation film having good optical uniformity. 10 minutes, more preferably 1 minute to 5 minutes.

<< C-5-4. Method for curing liquid crystal composition >>
In the step (step A-4) in which the liquid crystalline composition aligned in a homogeneous arrangement is irradiated with ultraviolet light and cured, the liquid crystalline composition may be cured by, for example, an ultrahigh pressure mercury lamp, dielectric Appropriate ones are selected from methods using an irradiation device using a body excimer discharge lamp, flash UV lamp, high pressure mercury lamp, low pressure mercury lamp, deep UV lamp, xenon lamp, xenon flash lamp, metal halide lamp, etc. obtain.

  Although the wavelength of the light source used for the ultraviolet light irradiation can be determined according to the wavelength region in which the polymerizable functional group of the liquid crystal compound used in the present invention has optical absorption, those having a wavelength of 210 nm to 380 nm are usually used. . More preferably, it is 250 nm to 380 nm. Further, the wavelength of the light source is preferably used by cutting a vacuum ultraviolet ray region of 100 nm to 200 nm with a filter or the like in order to suppress the photodecomposition reaction of the liquid crystal compound. If it is said range, a liquid crystalline composition will fully bridge | crosslink by a polymerization reaction, and the retardation film excellent in mechanical strength can be obtained.

Preferably the irradiation light amount of the ultraviolet light, the value measured at a wavelength of 365nm is a ^{30mJ / cm 2 ~1000mJ / cm 2} , more preferably from ^{50mJ / cm 2 ~800mJ / cm 2} , particularly preferably 100mJ / Cm ^{2 to} 500 mJ / cm ² . When the irradiation light quantity is in the above range, the liquid crystalline composition is sufficiently crosslinked by a polymerization reaction, and a retardation film having excellent mechanical strength can be obtained.

  The temperature in the irradiation apparatus (also referred to as irradiation temperature) during irradiation with the ultraviolet light is preferably kept below the liquid crystal phase-isotropic phase transition temperature (Ti) of the liquid crystalline composition. More preferably, it is the range of Ti-5 degrees C or less, Most preferably, it is the range of Ti-10 degrees C or less. Specifically, the irradiation temperature is preferably 15 ° C to 90 ° C, more preferably 15 ° C to 60 ° C. If it is said temperature range, a highly uniform retardation film can be produced.

  Examples of the method for maintaining the irradiation temperature constant (also referred to as temperature control means) include, for example, an air circulation type constant temperature oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, and heating for temperature adjustment. An appropriate one can be appropriately selected from a heating method such as a roll, a heat pipe roll or a metal belt or a temperature control method.

<< D. Positive C plate
In this specification, the positive C plate means that the in-plane main refractive index is nx (slow axis direction), ny (fast axis direction), and the refractive index in the thickness direction is nz. An element exhibiting positive uniaxiality satisfying nz> nx = ny. An element exhibiting positive uniaxiality ideally has an optical axis in the normal direction. In the present specification, nx = ny includes not only the case where nx and ny are completely the same, but also the case where nx and ny are substantially the same. Here, “when nx and ny are substantially the same” includes a case where the in-plane retardation value (Re [590]) is 10 nm or less.

<< D-1. Optical properties of positive C plate >>
Re [590] of the positive C plate used in the present invention is preferably 0 nm to 5 nm, and more preferably 0 nm to 2 nm. By setting it as said range, the contrast ratio of the diagonal direction of a liquid crystal display device can be raised.

  Rth [590] of the positive C plate used in the present invention is preferably −200 nm to −30 nm, more preferably −180 nm to −40 nm, particularly preferably −150 nm to −50 nm, and most preferably -130 nm to -70 nm. By setting it as said range, the contrast ratio of the diagonal direction of a liquid crystal display device can be raised.

  The transmittance of the positive C plate measured with light having a wavelength of 590 nm at 23 ° C. is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more.

<< D-2. Positioning means for positive C plate >>
Referring to FIG. 2, as a method for disposing the positive C plate 13 between the positive A plate 12 and the liquid crystal cell 20, an appropriate method can be appropriately selected according to the purpose. Preferably, the positive C plate 11 is provided with an adhesive layer or a pressure-sensitive adhesive layer (not shown) on both sides thereof, and is adhered to the surfaces of the positive A plate 12 and the liquid crystal cell 20. By filling the gaps between the optical elements with the adhesive layer or the pressure-sensitive adhesive layer in this way, the optical axes of the optical elements can be prevented from shifting when they are incorporated into a liquid crystal display device, Can be prevented from being rubbed and damaged. Further, the interface reflection between the layers of each optical element can be reduced, and the contrast can be increased when used in a liquid crystal display device.

  The thickness of the pressure-sensitive adhesive layer or adhesive layer and the type of adhesive or pressure-sensitive adhesive forming the pressure-sensitive adhesive layer or adhesive layer are as described in the above section C-2.

  In the positive C plate 13, when nx and ny are completely the same, no phase difference value is generated in the plane, so that the slow axis is not detected, the absorption axis of the polarizer 11, the slow axis of the positive C plate 13 is detected. The phase axis and the alignment direction of the liquid crystal molecules in the liquid crystal cell 20 can be arranged. Even if nx and ny are substantially the same, a slow axis may be detected if nx and ny are slightly different. In this case, the positive C plate 13 is preferably arranged so that its slow axis is substantially parallel or orthogonal to the absorption axis of the polarizer 11. In this specification, “substantially parallel” includes a case where the angle formed by the slow axis of the positive C plate 13 and the absorption axis of the polarizer 11 is 0 ° ± 2.0 °. The angle is preferably 0 ° ± 1.0 °, and more preferably 0 ° ± 0.5 °. The term “substantially orthogonal” includes the case where the angle formed by the slow axis of the positive C plate 13 and the absorption axis of the polarizer 11 is 90 ° ± 2.0 °, preferably 90 °. ± 1.0 °, more preferably 90 ° ± 0.5 °. As the degree of deviation from these angular ranges increases, the contrast tends to decrease when used in a liquid crystal display device.

<< D-3. Composition of positive C plate >>
The configuration (laminated structure) of the positive C plate is not particularly limited as long as it satisfies the optical characteristics described in the above section D-1. Specifically, the positive C plate may be a retardation film alone or a laminate composed of two or more retardation films. Preferably, the positive C plate is a single retardation film. This is because the shift and unevenness of the retardation value due to the contraction stress of the polarizer and the heat of the backlight can be reduced, and the liquid crystal panel can be made thin. When the positive C plate is a laminate, an adhesive layer or a pressure-sensitive adhesive layer may be included. When the laminate includes two or more retardation films, these retardation films may be the same or different. The details of the retardation film will be described later in section D-4.

  Rth [590] of the retardation film used for the positive C plate can be appropriately selected depending on the number of retardation films used. For example, when the positive C plate is composed of a retardation film alone, it is preferable that Rth [590] of the retardation film is equal to Rth [590] of the positive C plate. Therefore, the retardation value of the adhesive layer or the pressure-sensitive adhesive layer used when the positive C plate is laminated on the positive A plate or the liquid crystal cell is preferably as small as possible. For example, when the positive C plate is a laminate including two or more retardation films, the sum of Rth [590] of each retardation film is equal to Rth [590] of the positive C plate. It is preferable to design as follows. Specifically, when a positive C plate having Rth [590] of −100 nm is produced by laminating two retardation films, Rth [590] of each retardation film is set to −50 nm. Can do. Alternatively, Rth [590] of one retardation film can be set to −160 nm, and Rth [590] of the other retardation film can be set to 60 nm. When two retardation films are laminated, it is preferable to arrange the retardation films so that the slow axes of the respective retardation films are orthogonal to each other. This is because the in-plane retardation value (Re [590]) can be reduced. Here, for the sake of simplicity, only the case where the number of retardation films is two or less is shown, but it goes without saying that the present invention can also be applied to a laminate including three or more retardation films.

  The total thickness of the positive C plate is preferably 1 μm to 20 μm, more preferably 1.2 μm to 10 μm, and particularly preferably 1.5 μm to 5 μm. The said optical element can contribute to thickness reduction of a liquid crystal display device by setting it as the range of said thickness.

<< D-4. Retardation Film Used for Positive C Plate >>
As the retardation film used for the positive C plate, a film excellent in transparency, mechanical strength, thermal stability, moisture shielding property and the like is preferably used. Preferably, the positive C plate includes a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition oriented in a homeotropic alignment. In this specification, “homeotropic alignment” refers to a state in which liquid crystal compounds contained in a liquid crystalline composition are aligned in parallel and uniformly with respect to the film normal direction. There is no restriction | limiting in particular as a liquid crystalline composition and a liquid crystal compound used for the said positive C plate, For example, the thing as described in the C-4 term is mentioned.

  The liquid crystalline composition is not particularly limited as long as it contains a liquid crystal compound and exhibits liquid crystallinity. The content of the liquid crystal compound in the liquid crystal composition is preferably 40 to 100 (weight ratio), more preferably 50 to 99 (weight ratio) with respect to the total solid content 100 of the liquid crystal composition. And particularly preferably 70 to 98 (weight ratio). In the liquid crystalline composition, various additives such as a solvent, a leveling agent, a polymerization initiator, an alignment agent, a heat stabilizer, a lubricant, a lubricant, a plasticizer, and an antistatic agent are used within the range not impairing the object of the present invention. May be included.

  As the liquid crystal composition, those containing the same liquid crystal compound as described in the above section C-4 are used. The retardation film used for the positive C plate is preferably a liquid crystalline composition containing a liquid crystal compound described in JP-A No. 2002-174725, wherein the liquid crystalline composition is aligned in a homeotropic alignment. Or it is a hardened layer. More preferably, it is a liquid crystalline composition containing a polymer liquid crystal represented by the following general formula (3), which is a solidified layer or a cured layer in which the liquid crystalline composition is aligned in a homeotropic alignment. Particularly preferably, the liquid crystal includes a polymer liquid crystal represented by the following general formula (3), and a low molecular liquid crystal having one or more mesogenic groups and two or more polymerizable functional groups in a part of the molecular structure. A cured layer in which the liquid crystalline composition is aligned in a homeotropic alignment. With such a liquid crystalline composition, a retardation film having excellent optical uniformity and high transparency can be obtained.

In the formula, l is an integer of 14 to 20, and when the sum of m and n is 100, m is 50 to 70 and n is 30 to 50.

The content of the polymer liquid crystal represented by the following general formula (1) in the liquid crystal composition is preferably 10 to 100 (weight ratio) with respect to the total solid content 100 of the liquid crystal composition, and further Preferably it is 10-60 (weight ratio), Most preferably, it is 10-40 (weight ratio).
<< D-5. Method for producing retardation film used for positive C plate >>
Preferably as a method for producing a retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition aligned in a homeotropic alignment, (Step B-1) vertical alignment on the surface of a substrate (also referred to as a temporary support) (Step B-2): Applying a solution or dispersion of the liquid crystalline composition to the surface of the substrate subjected to the vertical alignment treatment, and aligning the liquid crystalline composition in a homeotropic arrangement And (step B-3) a step of drying and solidifying the liquid crystalline composition. More preferably, in the production method of the present invention, after (Step B-1) to (Step B-3), (Step B-4) a step of irradiating ultraviolet rays to cure the liquid crystalline composition, including. In general, the substrate is peeled off before the retardation film is put into practical use.

  FIG. 6 is a schematic diagram illustrating an outline of a method for producing a retardation film used for a positive C plate as an example of a preferred embodiment. In this step, the base material 402 is supplied from the feeding unit 401 and conveyed by the guide roll 403, and the solution or dispersion liquid of the alignment agent is applied in the first coater unit 404. The base material coated with the alignment agent is sent to the first drying means 405, and the alignment film is formed by evaporating the solvent. Next, the base material 406 on which the alignment film is formed is coated with a solution or dispersion liquid of the liquid crystalline composition in the second coater unit 407, and the solvent is evaporated in the second drying means 408. Then, a solidified layer of the liquid crystal composition aligned in the homeotropic alignment is formed. Next, the base material 409 on which the solidified layer of the liquid crystalline composition oriented in the homeotropic alignment is formed is sent to the ultraviolet irradiation unit 411, and the surface of the solidified layer is irradiated with ultraviolet light, so that the homeotropic alignment is achieved. A cured layer of the aligned liquid crystal composition is formed. The ultraviolet irradiation unit 411 typically includes an ultraviolet lamp 412 and a temperature control unit 410. Next, the base material on which the cured layer is formed is wound up by the winding unit 413 and used for the manufacturing process of the polarizing element. In addition, the said base material 402 can substitute the base material in which the solidified layer or hardened layer of the liquid crystalline composition orientated in the homogeneous arrangement | sequence described by the C-5 term was formed. In this case, a part of the sticking process described later is omitted, and productivity can be improved.

<< D-5-1. Vertical alignment treatment >>
In the step of performing the vertical alignment treatment on the surface of the substrate (step B-1), the vertical alignment treatment is used for aligning the liquid crystalline composition in a homeotropic alignment. As the vertical alignment treatment, an appropriate method can be appropriately selected according to the purpose. As a specific example, there is a method of forming an alignment film (also referred to as an alignment agent layer) by adsorbing an alignment agent on the surface of the substrate. This is because a retardation film having extremely few alignment defects (disclination) of the liquid crystal composition can be produced.

  As a method for adsorbing the alignment agent on the surface of the substrate, the same method as described in the section C-5-1 is used. The “solution coating method” is preferably a method in which an alignment film is formed by applying a solution or dispersion of an alignment agent to the surface of a substrate and drying it. It is because it is excellent in continuous productivity, workability, and economical efficiency, and the liquid crystalline composition can be uniformly aligned.

  Any appropriate alignment agent used for the vertical alignment treatment can be selected. Specific examples include lecithin, stearic acid, hexadecyltrimethylammonium bromide, octadecylamine hydrochloride, monobasic chromium complex (eg, myristic acid chromium complex, perfluorononanoic acid chromium complex, etc.), organic silane (example: Silane coupling agent, siloxane, etc.), perfluorodimethylcyclohexane, tetrafluoroethylene, polytetrafluoroethylene and the like. Particularly preferred as the aligning agent is organosilane. This is because it is excellent in workability, product quality, and alignment ability of the liquid crystal compound. Specific examples of the organic silane alignment agent include an alignment agent mainly composed of tetraethoxysilane [Corcoat Co., Ltd., trade name “ethyl silicate”].

  As a method for preparing the alignment agent solution or dispersion, a commercially available alignment agent solution or dispersion may be used, or a solvent may be further added to the commercially available alignment agent solution or dispersion. . Further, the solid content of the alignment agent may be dissolved in various solvents and used, or the alignment agent, various additives, and a solvent may be mixed and dissolved.

  The total solid content concentration of the solution of the aligning agent varies depending on solubility, coating viscosity, wettability on the substrate, thickness after coating, etc. -20 (weight ratio), more preferably 0.5 to 10 (weight ratio), particularly preferably 1 to 5 (weight ratio). If it is said range, a phase difference film with high surface uniformity can be obtained.

<< D-5-2. Method for applying liquid crystal composition solution or dispersion liquid >>
(Step B-2) In the step of applying a solution or dispersion of a liquid crystalline composition to the surface of the substrate that has been subjected to the vertical alignment treatment, and aligning the liquid crystalline composition in a homeotropic alignment, As the type of base material and the material forming the base material, appropriate materials can be appropriately selected from those described in the section C-5-2. Preferably, the substrate is a polymer substrate. This is because the surface smoothness of the base material and the wettability of the liquid crystal composition are excellent, and continuous production with a roll is possible, and the productivity can be greatly improved.

  As a method of preparing a liquid crystal composition solution or dispersion, a commercially available liquid crystal composition solution or dispersion may be used, and a solvent is further added to the commercially available liquid crystal composition solution or dispersion. May be used. Further, the solid content of the liquid crystalline composition may be used by dissolving it in various solvents, or an aligning agent, various additives, and a solvent may be mixed and dissolved.

  The total solid content concentration of the liquid crystal composition solution varies depending on the solubility, coating viscosity, wettability on the substrate, thickness after coating, etc. -100 (weight ratio), more preferably 30-80 (weight ratio), particularly preferably 40-60 (weight ratio). If it is said range, a phase difference film with high surface uniformity can be obtained.

  As the type of the solvent and the method for applying the solution or dispersion of the liquid crystalline composition, an appropriate one can be appropriately selected from those described in the section C-5-2. Preferably, the solvent is at least one solvent selected from cyclopentanone, cyclohexanone, methyl isobutyl ketone, methyl ethyl ketone, toluene, ethyl acetate and tetrahydrofuran. These solvents are preferable because they do not cause erosion that has a practically adverse effect on the substrate and can sufficiently dissolve the above composition.

<< D-5-3. Method for drying liquid crystal composition >>
In the step (step B-3) of drying and solidifying the liquid crystalline composition aligned in the homeotropic alignment, a method for drying the liquid crystalline composition, a drying temperature, and a drying time are C-5. Appropriate ones can be selected as appropriate from the same conditions and conditions as described in Section -4.

<< D-5-3. Method for curing liquid crystal composition >>
(Step B-4) In the step of irradiating and curing the liquid crystalline composition oriented in the homeotropic alignment, the method of curing the liquid crystalline composition, the wavelength of the light source, the irradiation light amount, the irradiation temperature As the drying method, an appropriate method can be appropriately selected from the same conditions and conditions as those described in the section C-5-4.

<< E-1. Manufacturing method of polarizing element >>
The order of bonding the polarizer, positive A plate, and positive C plate is not particularly limited as long as the present invention is satisfied. For example, a polarizer, a positive A plate, and a positive C plate may be stacked in this order, or a positive C plate, a positive A plate, and a polarizer may be stacked in this order.

  FIG. 7 is a schematic diagram illustrating an outline of a polarizing element manufacturing process (polarizer and positive A plate bonding process) as an example of a preferred embodiment. In this step, a substrate 501 provided with a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement is supplied from a first feeding unit 501, conveyed by a guide roll 503, and the solidified in the coater unit 504. An adhesive or a pressure-sensitive adhesive is applied to the surface of the layer or the cured layer. The base material coated with the adhesive or the pressure-sensitive adhesive is sent to the drying means 505, and the solvent is evaporated to form the adhesive layer or the pressure-sensitive adhesive layer. Next, a substrate including the adhesive layer or the pressure-sensitive adhesive layer and a solidified layer or a cured layer of the liquid crystalline composition aligned in a homogeneous arrangement includes a polarizer 506 supplied from the second feeding unit 509, Laminate rolls 507 and 508 are pressure-bonded so that the solidified layer or the cured layer is in contact with the polarizer 506. At this time, the base material 511 is peeled off and wound up by the first winding portion 510. A laminated body 512 including a polarizer, an adhesive layer or a pressure-sensitive adhesive layer, and a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement is wound up by a second winding unit 513. Note that the stacked body of the stacked body 512 and the positive C plate can also be attached by the same method as described here.

  The method of bonding each of the polarizer, the positive A plate, and the positive C plate is not limited to the illustrated example, and any appropriate method can be adopted. Specific examples include hot melt lamination, non-solvent lamination, wet lamination, dry lamination, and the like. In the present invention, dry lamination is preferably used as shown in FIG. This is because a polarizing element having excellent adhesiveness and workability and good appearance uniformity can be obtained. In the present specification, “dry lamination” refers to applying a solution or dispersion of an adhesive (or pressure-sensitive adhesive) to one film and then evaporating and drying the solvent with a drying means. A method of pressure bonding with a film and a laminate roll.

  As the method for applying the adhesive or pressure-sensitive adhesive, an appropriate one can be appropriately selected depending on the type, thickness, viscosity, and the like of the adhesive or pressure-sensitive adhesive. Specifically, the same method as that described in the section C-5-2 can be used.

  The drying temperature of the adhesive or pressure-sensitive adhesive is preferably 30 ° C to 180 ° C, more preferably 40 ° C to 150 ° C, and particularly preferably 50 ° C to 130 ° C. If it is said range, the adhesive bond layer or adhesive layer excellent in surface uniformity can be obtained.

  Arbitrary appropriate drying time can be employ | adopted as drying time of the said adhesive agent or an adhesive. The drying time is preferably 1 minute to 20 minutes, more preferably 1 minute to 15 minutes, and particularly preferably 1 to 10 minutes. This is because, within the above range, an adhesive layer or a pressure-sensitive adhesive layer excellent in surface uniformity is obtained, and as a result, the durability of the polarizing element is improved.

<< F. LCD panel >>
The polarizing element of the present invention is preferably disposed on one side or both sides of a liquid crystal cell and used as a liquid crystal panel. Preferably, the polarizing element is disposed on the viewing side of the liquid crystal cell in order to greatly increase the contrast in the oblique direction of the liquid crystal display device. The type of the liquid crystal cell is not particularly limited, and any of a transmissive type, a reflective type, and a reflective transflective type can be used. Examples of the driving mode of the liquid crystal cell include a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a horizontal alignment (ECB) mode, a vertical alignment (VA) mode, and an in-plane switching (IPS) mode. , Bend nematic (OCB) mode, hybrid alignment (HAN) mode, ferroelectric liquid crystal (SSFLC) mode, antiferroelectric liquid crystal (AFLC) mode, and the like. Preferably, the polarizing element of the present invention is used for an IPS mode, VA mode, or OCB mode liquid crystal cell.

  The twisted nematic (TN) mode liquid crystal cell is one in which a nematic liquid crystal having positive dielectric anisotropy is sandwiched between two substrates, and the liquid crystal molecules are aligned by the surface alignment treatment of the glass substrate. The one twisted 90 degrees. Specific examples include the liquid crystal cell described in “Liquid Crystal Dictionary” on page 158 (1989) and the liquid crystal cell described in JP-A-63-279229.

  The vertical alignment (VA) mode liquid crystal cell uses a voltage-controlled birefringence (ECB) effect, and nematic liquid crystal having a negative dielectric anisotropy between transparent electrodes when no voltage is applied. Means a vertically aligned liquid crystal cell. Specific examples include liquid crystal cells described in JP-A-62-210423 and JP-A-4-153621. In addition, as described in JP-A No. 11-258605, the VA mode liquid crystal cell includes a substrate provided with a slit in a pixel or a substrate on which a protrusion is formed in order to enlarge a viewing angle. By using it, it may be a multi-domain MVA mode liquid crystal cell. Further, as described in JP-A-10-123576, a VATN mode liquid crystal in which a chiral agent is added to a liquid crystal, the liquid crystal is substantially vertically aligned when no nematic liquid crystal voltage is applied, and twisted multi-domain alignment is applied when a voltage is applied. It may be a cell.

  The in-plane switching (IPS) mode liquid crystal cell is a so-called sandwich cell in which a liquid crystal is sealed between two parallel substrates using a voltage-controlled birefringence (ECB) effect. A liquid crystal which responds to a nematic liquid crystal that is homogeneously aligned in the absence of an electric field (also referred to as a transverse electric field) parallel to the substrate. Specifically, Techno Times Publishing “Monthly Display July” p. 83-p. 88 (1997 edition) and “Liquid Crystal vol. 2 No. 4” published by the Japanese Liquid Crystal Society. 303-p. 316 (1998 edition), when the upper and lower polarizing plates are arranged orthogonally so that the major axis of the liquid crystal molecules and the polarizing axis of the incident side polarizing plate coincide with each other, the display is completely black without an electric field. When there is an electric field, the liquid crystal molecules are those that can obtain transmittance according to the rotation angle by rotating while keeping parallel to the substrate.

  The liquid crystal cell of the above-mentioned bend nematic (OCB: Optically Compensated Bend or Optically Compensated Birefringence) mode is a voltage-controlled birefringence (ECB: Electrically controlled birefringence effect using a positive birefringence effect). The liquid crystal is a bend-aligned liquid crystal cell in which twisted alignment exists in the center when no voltage is applied. The OCB mode liquid crystal cell is also referred to as a “π cell”. Specific examples include those described in Kyoritsu Publishing Co., Ltd. “Next Generation Liquid Crystal Display” (2000), pages 11 to 27, and those described in JP-A-7-084254.

  FIG. 8 is a schematic perspective view of a liquid crystal panel according to a preferred embodiment of the present invention. The liquid crystal panel 600 includes a liquid crystal cell 20, a polarizing element 10 disposed on one side of the liquid crystal cell 20, a polarizer 11 ′ disposed on the other side of the liquid crystal cell, and a retardation film 14. . The polarizers 11 and 11 'are arranged so that their absorption axes are orthogonal to each other. The retardation film 14 is appropriately selected or omitted depending on the driving mode of the liquid crystal cell. Preferably, the retardation film 14 has a retardation value that cancels the in-plane and / or thickness direction retardation value of the liquid crystal cell 20. Further, preferably, the retardation film 14 is disposed adjacent to the liquid crystal cell 20 as shown in (a) and (b) of FIG. 8. The polarizing element 10 includes a polarizer 11, a positive A plate 12, and a positive C plate 13 in this order. The slow axis of the positive A plate 12 is orthogonal to the absorption axis of the polarizer 11. Preferably, the polarizing element 10 is disposed on the viewing side of the liquid crystal cell 20.

  The liquid crystal cell 20 includes a pair of glass substrates and a liquid crystal layer as a display medium disposed between the substrates (none of which is shown). One glass substrate (active matrix substrate) includes an active element (typically a TFT) for controlling the electro-optic effect of the liquid crystal, a scanning line for supplying a gate signal to the active element, and a signal line for supplying a source signal. Provided (none shown). The other glass substrate (color filter substrate) is provided with a colored layer as a color filter, a light shielding layer (also referred to as a black matrix), and an ITO layer (all not shown). The distance (cell gap) between the two glass substrates is controlled by a spacer (not shown). For example, an alignment film (not shown) made of polyimide is provided on the side of the glass substrate in contact with the liquid crystal layer.

<< G. Liquid crystal display device >>
The polarizing element and the liquid crystal panel of the present invention include liquid crystal display devices such as personal computers, liquid crystal televisions, mobile phones, and personal digital assistants (PDAs), organic electroluminescence displays (organic EL), projectors, projection televisions, plasma televisions, and the like. It can be used for an image display device. Especially, the polarizing element and liquid crystal panel of this invention are used suitably for a liquid crystal display device, and are used especially suitably for a liquid crystal television.

  FIG. 9 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. The liquid crystal display device 700 includes a liquid crystal panel 600 including the polarizing element of the present invention, protective layers 30 and 30 ′ disposed on both sides of the liquid crystal panel 600, and a surface disposed further outside the protective layers 30 and 30 ′. The processing layers 40 and 40 ′, and the brightness enhancement film 50, the prism sheet 60, the light guide plate 70, and the backlight 80 disposed outside the surface processing layer 40 ′ (backlight side). As the surface treatment layers 40 and 40 ′, treatment layers subjected to hard coat treatment, antireflection treatment, antisticking treatment, diffusion treatment (also referred to as antiglare treatment), and the like are used. Moreover, as the said brightness enhancement film 50, the polarization separation film (Example: Sumitomo 3M Co., Ltd. brand name "D-BEF series") etc. which have a polarization selection layer are used. By using these optical members, a display device with higher display characteristics can be obtained. Moreover, in another embodiment, as long as the optical member illustrated in FIG. 9 satisfies the present invention, a part of the optical member is omitted depending on the driving mode and application of the liquid crystal cell used, or others. The optical member can be replaced.

  The contrast ratio (YW / YB) in the azimuth angle 45 ° direction and polar angle 60 ° direction of the liquid crystal display device provided with the liquid crystal panel of the present invention is preferably 10 to 200, more preferably 15 to 200, particularly. Preferably it is 40-200.

The present invention will be further described using the above examples and comparative examples. In addition, this invention is not limited only to these Examples. In addition, each analysis method used in the Example is as follows.
(1) Measuring method of single transmittance and polarization degree of polarizer:
It measured at 23 degreeC using the spectrophotometer [Murakami Color Research Laboratory Co., Ltd. product name "DOT-3"].
(2) Measuring method of thickness:
When the thickness was less than 10 μm, measurement was performed using a thin film spectrophotometer [manufactured by Otsuka Electronics Co., Ltd., “instant multiphotometry system MCPD-2000”]. When the thickness was 10 μm or more, measurement was performed using an Anritsu digital micrometer “KC-351C type”.
(3) Measuring method of phase difference values (Re, Rth):
It measured with the light of wavelength 590nm in 23 degreeC using the phase difference meter [Oji Scientific Instruments Co., Ltd. product name "KOBRA21-ADH"] based on a parallel Nicol rotation method. Note that the average value and variation of the phase difference values were obtained by preparing samples as shown in FIG. 10 and measuring Re [590] at nine locations in the plane at equal intervals.
(4) Measuring method of refractive index of film:
It calculated | required from the refractive index measured with the light of wavelength 589nm in 23 degreeC using the Abbe refractometer [The product name "DR-M4" by Atago Co., Ltd.].
(5) Transmittance measurement method:
It measured with the light of wavelength 590nm in 23 degreeC using the ultraviolet visible spectrophotometer [The product name "V-560" by JASCO Corporation].
(6) Measuring method of photoelastic coefficient:
Using a spectroscopic ellipsometer [product name “M-220” manufactured by JASCO Corporation], the sample (size 2 cm × 10 cm) is sandwiched at both ends and stress (5 to 15 N) is applied to the phase difference at the center of the sample. The value (23 ° C./wavelength 590 nm) was measured and calculated from the slope of the function of stress and retardation value.
(7) Measuring method of contrast ratio of liquid crystal display device:
It measured in the dark room of 23 degreeC using the following methods, a liquid crystal cell, and a measuring apparatus. A white image and a black image were displayed on the liquid crystal display device, and the Y value of the XYZ display system in the azimuth angle 45 ° direction and polar angle 60 ° direction of the display screen was measured by a product name “EZ Contrast 160D” manufactured by ELDIM. Then, the contrast ratio “YW / YB” in the oblique direction was calculated from the Y value (YW) in the white image and the Y value (YB) in the black image. An azimuth angle of 45 ° represents an azimuth rotated 45 ° counterclockwise when the long side of the panel is 0 °, and a polar angle of 60 ° is when the front direction of the display screen is 0 °. Represents a direction inclined at an angle of 60 °.
・ Liquid crystal cell: Installed in SONY KLV-17HR2 ・ Panel size: 375mm x 230mm

<Synthesis of liquid crystal compounds>
[Production Example 1]
4- (4-propylcyclohexyl) phenol (53.60 g, 0.25 mol), 2-chloroethanol (59.30 g, 0.74 mol), potassium carbonate (101.70 g, 0.74 mol), potassium iodide (12 .20 g, 73.6 mmol) and N, N-dimethylformamide (250 mL) were mixed in an eggplant flask and kept at 90 ° C. and stirred for 8 hours. After adding ethyl acetate (400 mL) to the above reaction solution, the organic phase mainly composed of ethyl acetate was washed 3 times with water (300 mL × 3 times), once with saturated brine (50 mL), and then with magnesium sulfate. Dehydrated. Ethyl acetate was removed from the organic phase under reduced pressure to obtain a light brown crude product. The crude product was recrystallized from hexane and dried to obtain 42.6 g (yield: 66% by weight) of 2- [4- (4-propylcyclohexyl) phenoxy] ethanol as white crystals.

  2- [4- (4-propylcyclohexyl) phenoxy] ethanol (30.20 g, 0.12 mol), dehydrated tetrahydrofuran (120 mL) containing BHT in a trace amount as a polymerization inhibitor, triethylamine (32.1 mL, 0.23 mol). The mixture was mixed in a 500 mL three-necked flask and cooled with ice water while stirring. Distilled acrylic acid chloride (14.6 ml, 0.18 mol) was added in small portions and stirred for 8 hours while maintaining the temperature at room temperature. The reaction solution was poured into 500 mL of saturated saline, and 1N hydrochloric acid was added thereto until the reaction solution became acidic (pH 1 to 4). The reaction solution was extracted with ethyl acetate (400 mL × twice), and an organic phase mainly composed of ethyl acetate was collected. The organic phase was washed three times with water (300 mL × 3 times), once with saturated brine (50 mL), and dehydrated with magnesium sulfate. Ethyl acetate was removed from the organic phase under reduced pressure to obtain a crude product. Thereafter, the crude product was purified by silica gel column chromatography using dichloromethane as a developing solvent, dichloromethane was removed under reduced pressure, and a liquid crystal compound (I) represented by the following formula (4) of white crystals was obtained as 30. 0.6 g (yield: 84% by weight) was obtained.

The nuclear magnetic resonance spectrum data ( ¹ H-NMR) of the compound represented by the formula (4) is shown below. Here, measurement of ¹ H-NMR uses JEOL Co., Ltd. (LA400), a small amount of sample: observation nucleus: 1H, frequency: 400 MHz, pulse width: 45 degrees, pulse repetition time: 10 seconds Chemical shift standard: 7.25 ppm, measurement solvent: deuterated chloroform, measurement temperature: measured at room temperature.
¹ H-NMR (400 Hz, CDCl ₂ ): δ 0.89 (t, 3H, J = 7.2 Hz), 0.97-1.08 (m, 2H), 1.17-1.45 (m, 7H), 1.81-1.88 (m, 4H), 2.40 (tt, 1H, J = 3.2, 12.2 Hz), 4.18 (t, 2H, J = 4.8 Hz), 4.49 (t, 2H, J = 4.8 Hz), 5.84 (dd, 1H, J = 1.2, 10.3 Hz), 6.15 (dd, 1H, J = 10.3, 17. 4 Hz), 6.43 (dd, 1H, J = 1.2, 17.4 Hz), 6.82-6.86 (m, 2H), 7.09-7.14 (m, 2H)

<< Preparation of photo-alignment film >>
[Production Example 2]
Alignment agent containing a compound having a cinnamate group on the surface of a commercially available polyethylene terephthalate film [trade name “S-27E” (thickness: 75 μm) manufactured by Toray Industries, Inc., trade name “Staralign 2100” (total solid content) Concentration: 2 wt%)] was applied using a gravure coater and dried for 2 minutes in an air circulation type thermostatic oven at 90 ° C. ± 1 ° C. to form a photo-alignment film having a thickness of 0.3 μm. Next, using a high-pressure mercury lamp as a light source and an ultraviolet irradiation device equipped with a wire grid polarizer (having a polarization separation function at a wavelength of 210 nm to 380 nm), the surface of the photo-alignment film is formed in an air atmosphere at 30 ° C. , 100 mJ / cm ² (measured at a wavelength of 310 nm) is irradiated with polarized ultraviolet light so that the electric field vector of the polarized ultraviolet light is orthogonal to the longitudinal direction of the film and subjected to horizontal alignment treatment. did.

<Production of polarizer>
[Reference Example 1]
Polymer film mainly composed of polyvinyl alcohol [Kuraray Co., Ltd., trade name “9P75R (thickness: 75 μm, average polymerization degree: 2,400, saponification degree 99.9 mol%)”] at 30 ° C. ± 3 ° C. In a dyeing bath containing iodine and potassium iodide held, the film was uniaxially stretched 2.5 times while dyeing using a roll stretching machine. Subsequently, it was uniaxially stretched so as to be 6 times the original length of the polyvinyl alcohol film while performing a crosslinking reaction in an aqueous solution containing boric acid and potassium iodide maintained at 60 ± 3 ° C. The obtained film was dried in an air-circulating constant temperature oven at 50 ° C. ± 1 ° C. for 30 minutes to obtain a polarizer having a moisture content of 26%, a thickness of 28 μm, a polarization degree of 99.9%, and a single transmittance of 43.5%. Obtained.

<< Preparation of positive A plate >>
[Reference Example 2]
35 parts by weight of the liquid crystal compound (I) obtained in Production Example 1, 60 parts by weight of a liquid crystal compound [trade name “PariocolorLC242” manufactured by BASF Corp.], Trisacryloyloxyethyl phosphate [manufactured by Osaka Organic Chemical Industry Co., Ltd.] 5 parts by weight of the name “Biscoat 3PA”, 3 parts by weight of a photopolymerization initiator [trade name “Irgacure 907” manufactured by Ciba Specialty Chemicals Co., Ltd.], and 0 for a leveling agent [trade name “BYK361” manufactured by Big Chemie] .05 parts by weight of a mixed liquid crystal composition (containing 92 (weight ratio) of the liquid crystal compound with respect to the liquid crystal composition 100) dissolved in 200 parts by weight of cyclopentanone (boiling point 131 ° C.) Adjusted.

Next, the above solution was applied to the surface of the photo-alignment film of the base material provided with the photo-alignment film prepared in Production Example 2 using a rod coater, and 3 in an air circulation type thermostatic oven at 90 ° C. ± 1 ° C. The solidified layer of the liquid crystalline composition was dried for minutes and aligned in a homogeneous arrangement. Next, under an air atmosphere at 30 ° C., the solidified layer is irradiated with ultraviolet rays having an irradiation light amount of 400 mJ / cm ² (measured at a wavelength of 365 nm), and the liquid crystal compound is cured by a polymerization reaction to form a homogeneous array. A cured layer of the aligned liquid crystal composition was formed. The cured layer of the liquid crystalline composition aligned in this homogeneous arrangement was used as a retardation film A. The properties of the retardation film A are as shown in Table 1.

[Reference Example 3]
100 parts by weight of a liquid crystal compound [trade name “UCL-001” manufactured by Dainippon Ink and Chemicals, Inc.], 3 parts by weight of a photopolymerization initiator [trade name “Irgacure 907” manufactured by Ciba Specialty Chemicals, Inc.], and A liquid crystalline composition (containing 97 (weight ratio) of a liquid crystal compound with respect to the liquid crystalline composition 100) in which 0.05 part by weight of a leveling agent [trade name “BYK361” manufactured by Big Chemie Co., Ltd.] was mixed with cyclopenta The solution was adjusted to 200 parts by weight of non (boiling point 131 ° C.). Next, the solution was applied, dried, and cured in the same manner as in Reference Example 2 to form a cured layer of a liquid crystalline composition that was aligned in a homogeneous alignment. A cured layer of the liquid crystalline composition aligned in the homogeneous arrangement was used as a retardation film B. The characteristics of the retardation film B are as shown in Table 1.

[Reference Example 4]
100 parts by weight of a liquid crystal compound [BASF Co., Ltd., trade name “Pariocolor LC242”], photopolymerization initiator [Ciba Specialty Chemicals Co., Ltd., trade name “Irgacure 907”], and a leveling agent [manufactured by Big Chemie] A liquid crystal composition mixed with 0.05 part by weight of the trade name “BYK361”] (containing 97 (weight ratio) of the liquid crystal compound with respect to the liquid crystal composition 100), cyclopentanone (boiling point 131 ° C.) The solution was adjusted to 200 parts by weight. Next, the solution was applied, dried, and cured in the same manner as in Reference Example 2 to form a cured layer of a liquid crystalline composition that was aligned in a homogeneous alignment. The cured layer of the liquid crystalline composition aligned in the homogeneous arrangement was used as a retardation film C. The characteristics of the retardation film C are as shown in Table 1.

[Reference Example 5]
Curing of the liquid crystalline composition that was applied, dried and cured in the same manner as in Reference Example 2 except that the coating thickness was changed using the solution prepared in Reference Example 2, and aligned in a homogeneous alignment. A layer was formed. A cured layer of the liquid crystalline composition aligned in the homogeneous arrangement was used as a retardation film X. The characteristics of the retardation film P are as shown in Table 1.

[Reference Example 6]
Commercially available polymer film mainly composed of polynorbornene [trade name “ZEONOR” (thickness: 100 μm) manufactured by Nippon Zeon Co., Ltd.] is fixed in the longitudinal direction of the film with a tenter stretching machine, and the air circulation type at 175 ° C. In a constant temperature oven (a temperature at a distance of 3 cm from the film back surface was measured, temperature variation ± 1 ° C.), the film was stretched uniaxially by 1.40 times in the width direction to produce a retardation film Q. The properties of the obtained retardation film Q are as shown in Table 1. In addition, Re [590] of the said polymer film (before extending | stretching) was 5 nm, and Rth [590] was 9 nm.

<< Preparation of positive C plate >>
[Reference Example 7]
Commercially available polyethylene terephthalate film [trade name “S-27E” manufactured by Toray Industries, Inc. (thickness: 75 μm)] and ethyl silicate solution [manufactured by Colcoat Co., Ltd. (mixed solution of ethyl acetate and isopropyl alcohol, total solid concentration: 2 wt. %)] Is coated with a gravure coater and dried in a 130 ° C. air-circulating constant temperature oven (temperature variation ± 1 ° C.) for 1 minute to produce a polyethylene terephthalate film having a glassy polymer film with a thickness of 0.1 μm. did.

5 parts by weight of a polymer liquid crystal (weight average molecular weight: 5,000) represented by the following formula (5), having a phenylbenzoate group as a mesogenic group, and having two polymerizable functional groups in the molecular structure 20 parts by weight of a low-molecular liquid crystal [manufactured by BSAF, trade name “Pariocolor LC242”] and 1.25 parts by weight of a photopolymerization initiator [manufactured by Ciba Specialty Chemicals, trade name “Irgacure 907”] are mixed. An aqueous composition was prepared and dissolved in 75 parts by weight of cyclohexanone to prepare a coating solution. The coating solution is coated on the glassy polymer film of the polyethylene terephthalate film using a rod coater, dried in an air circulation type thermostatic oven (temperature variation ± 1 ° C.) at 80 ° C. for 2 minutes, and then room temperature ( And a solidified layer of a liquid crystalline composition aligned in a homeotropic alignment was formed on the substrate. Next, using an irradiation apparatus using a metal halide lamp as a light source in an air atmosphere at 30 ° C., the surface of the solidified layer was irradiated with ultraviolet light having an irradiation light amount of 400 mJ / cm ² (measured at a wavelength of 365 nm). A cured layer of a liquid crystalline composition oriented in a homeotropic alignment was formed on the substrate. A cured layer of the liquid crystalline composition aligned in this homeotropic alignment was used as a retardation film D. The properties of the retardation film D are as shown in Table 2.

[Reference Example 8]
A retardation film E was produced in the same manner as in Reference Example 5 except that the coating thickness of the coating solution was changed. The properties of the retardation film E are as shown in Table 2.

[Reference Example 9]
A retardation film F was produced in the same manner as in Reference Example 5 except that the coating thickness of the coating solution was changed. The properties of the retardation film F are as shown in Table 2.

<< Production of IPS mode liquid crystal cell >>
[Reference Example 10]
The liquid crystal panel was taken out from the liquid crystal display device [SONY KLV-17HR2] including the IPS mode liquid crystal cell, the polarizing plates arranged above and below the liquid crystal cell were removed, and the glass surfaces (front and back) of the liquid crystal cell were washed. .

<Production of polarizing element>
[Example 1]
The surface of the polarizer produced in Reference Example 1 was coated with an isocyanate-based adhesive [trade name “Takenate 631” manufactured by Mitsui Takeda Chemical Co., Ltd.] using a fountain coater, and air circulation drying at 90 ° C. ± 1 ° C. It was dried in an oven for 3 minutes to form an adhesive layer having a thickness of 5 μm. Next, on the surface of the adhesive layer, the retardation film A produced in Reference Example 2 is set such that the slow axis of the retardation film A is orthogonal to the absorption axis of the polarizer (90 ° ± 0.5 °). Thus, the laminate was pressed with a laminate roll (at this time, the substrate was peeled off), and a laminate of the polarizer and the retardation film A was produced. Next, an isocyanate-based adhesive [trade name “Takenate 631” manufactured by Mitsui Takeda Chemical Co., Ltd.] was applied to the surface of the laminate with a fountain coater, and then in an air circulation drying oven at 90 ° C. ± 1 ° C. It was dried for 3 minutes to form an adhesive layer having a thickness of 5 μm. Next, the retardation film E produced in Reference Example 8 is formed on the surface of the adhesive layer so that the slow axis of the retardation film E is parallel to the absorption axis of the polarizer (0 ° ± 0.5 °). Thus, a polarizing element A was prepared by pressure bonding with a laminating roll (at this time, the substrate was peeled off), and a polarizer, a retardation film A, and a retardation film E in this order.

[Example 2]
In the same manner as in Example 1, a polarizing element B including a polarizer, a retardation film B, and a retardation film E in this order was produced.

[Example 3]
In the same manner as in Example 1, a polarizing element C including a polarizer, a retardation film C, and a retardation film E in this order was produced.

[Example 4]
In the same manner as in Example 1, a polarizing element D including a polarizer, a retardation film B, and a retardation film D in this order was produced.

[Example 5]
In the same manner as in Example 1, a polarizing element F including a polarizer, a retardation film B, and a retardation film F in this order was produced.

[Comparative Example 1]
In the same manner as in Example 1, a polarizing element X including a polarizer, a retardation film E, and a retardation film B in this order was produced. This polarizing element X is different only in that the lamination order of the retardation film B and the retardation film E in the polarizing element B of Example 2 is reversed.

[Example 6]
As shown in FIG. 11, the polarizing element B produced in Example 2 was attached to the surface on the viewing side of the liquid crystal cell produced in Reference Example 10 using an acrylic pressure-sensitive adhesive (thickness: 20 μm), and the liquid crystal On the backlight side of the cell, the acrylic adhesive (thickness: 20 μm) was prepared so that the polarizer produced in Reference Example 1 had an absorption axis perpendicular to the absorption axis of the polarizing element (90 ° ± 0.5 °). ) To prepare a liquid crystal panel B. The liquid crystal panel B was incorporated in the original liquid crystal display device, the backlight was turned on, and the contrast ratio in the oblique direction was measured 10 minutes later. The properties obtained are shown in Table 3.

[Example 7]
In the same manner as in Example 6, a liquid crystal panel A including the polarizing element A prepared in Example 1 on the surface on the viewing side of the liquid crystal cell and the polarizer on the backlight side was manufactured. The properties obtained are shown in Table 3.

[Example 8]
In the same manner as in Example 6, a liquid crystal panel C including a polarizing element C on the surface on the viewing side of the liquid crystal cell and a polarizer on the backlight side was produced. The properties obtained are shown in Table 3.

[Example 9]
In the same manner as in Example 6, a liquid crystal panel D provided with a polarizing element D on the surface on the viewing side of the liquid crystal cell and a polarizer on the backlight side was produced. The properties obtained are shown in Table 3.

[Example 10]
In the same manner as in Example 6, a liquid crystal panel E including a polarizing element E on the surface on the viewing side of the liquid crystal cell and a polarizer on the backlight side was produced. The properties obtained are shown in Table 3.

[Comparative Example 2]
The polarizer produced in Reference Example 1 was attached to the surface on the viewing side of the liquid crystal cell using an acrylic pressure-sensitive adhesive (thickness: 20 μm), and the polarization produced in Reference Example 1 on the backlight side of the liquid crystal cell. A liquid crystal panel I is manufactured by sticking the element with an acrylic adhesive (thickness: 20 μm) so that the absorption axis thereof is orthogonal to the absorption axis of the polarizing element (90 ° ± 0.5 °). did.

[Comparative Example 3]
In the same manner as in Example 6, a liquid crystal panel J provided with a polarizing element X on the surface on the viewing side of the liquid crystal cell and a polarizer on the backlight side was produced. The properties obtained are shown in Table 3.

[Evaluation]
As shown in Examples 6 to 10, a liquid crystal panel in which a polarizing element including a polarizer, a positive A plate, and a positive C plate in this order is arranged on the viewing side is a liquid crystal display device having a high contrast ratio in an oblique direction. I was able to get it. Further, by using a retardation film comprising a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement on the positive A plate, a thin polarizing element can be obtained. As a result, the thickness of the liquid crystal panel and the liquid crystal display device can be reduced. I was able to make it thinner. In consideration of Reference Examples 2 to 5, the retardation film composed of a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement used as a positive A plate has an in-plane birefringence index (Δn) of 0.04 to It can be seen that the smaller the range of 0.20, the smaller the in-plane retardation value (Re [590]) can be obtained. On the other hand, as shown in Reference Example 6, in the retardation film obtained by uniaxially stretching the polymer film with a tenter stretching machine, in addition to being thick (although having a slow axis in the film width direction), Rth [590] was larger than Re [590], and even a positive A plate could not be obtained.

  Comparative Example 2 is a liquid crystal panel in which no optical element is disposed and only a polarizer is disposed on both sides of the liquid crystal cell, but only a liquid crystal display device having a low contrast ratio in an oblique direction can be obtained. Comparative Example 3 is a liquid crystal panel using a polarizing element including a polarizer, a positive C plate, and a positive A plate in this order, in which the stacking order of the positive A plate and the positive C plate is reversed. In this case as well, only a liquid crystal display device having a low contrast ratio in the oblique direction could be obtained.

  As described above, according to the liquid crystal panel of the present invention, the contrast ratio in the oblique direction can be increased, so that it can be said that it is extremely useful for improving the display characteristics of the liquid crystal display device. The liquid crystal panel of the present invention is suitably used for a liquid crystal display device and a liquid crystal television.

It is a schematic sectional drawing of the polarizing element by preferable embodiment of this invention. It is a schematic sectional drawing explaining the typical example of preferable embodiment of the polarizing element of this invention including the positional relationship with a liquid crystal panel. It is a schematic diagram explaining the outline | summary of the typical alignment film formation process in the manufacturing method of this invention. It is a schematic diagram explaining the outline | summary of the coating / drying process of the typical liquid crystalline composition in the manufacturing method of this invention. It is a schematic perspective view of the typical ultraviolet irradiation part in the manufacturing method of this invention. It is a schematic diagram explaining the outline | summary of the manufacturing method of the retardation film used for the positive C plate by the preferable embodiment of this invention. It is a schematic diagram explaining the outline of the manufacturing process of the polarizing element by the preferable embodiment of this invention. 1 is a schematic perspective view of a liquid crystal panel according to a preferred embodiment of the present invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. It is the schematic of the sample for measuring the in-plane retardation value of the retardation film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measurement location 10 Polarizing element 11, 11 'Polarizer 12 Positive A plate 13 Positive C plate 20 Liquid crystal cell 30, 30' Protective layer 40, 40 'Surface treatment layer 50 Brightness enhancement film 60 Prism sheet 70 Light guide plate 80 Backlight 101 201, 401 Feeding unit 102, 202, 402, 502 Base material 103, 203, 403, 503 Guide roll 104, 204, 504 Coater unit 105, 205, 505 Drying unit 106, 206, 410 Temperature control unit 107, 207, 412 UV lamp 108, 303 Polarizing filter 109, 208, 411 UV irradiation unit 110, 209, 413 Winding unit 301 Dielectric excimer discharge lamp 302 Condensing mirror 404 First coater unit 407 Second coater unit 405 First Drying means 408 Second drying hand Step 501 First feeding unit 507, 508 Laminating roll 509 Second feeding unit 510 First winding unit 513 Second winding unit 600 Liquid crystal panel 700 Liquid crystal display device

Claims (9)

A liquid crystal composition comprising a polarizer, a positive A plate satisfying the following formula (1), and a positive C plate satisfying the following formula (2) in this order, wherein the positive A plate is aligned in a homogeneous array. A polarizing element comprising a retardation film comprising a solidified layer or a cured layer, wherein the slow axis of the positive A plate is substantially perpendicular to the absorption axis of the polarizer:
70 nm ≦ Re [590] ≦ 200 nm (1)
−200 nm ≦ Rth [590] ≦ −30 nm (2)
[However, Re [590] and Rth [590] are an in-plane retardation value and a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C., respectively. ].   The polarizing element of Claim 1 whose whole thickness of the said polarizing element is 20 micrometers-60 micrometers.   Refractive index (ne) of extraordinary light and refractive index (no) of ordinary light measured with light having a wavelength of 589 nm at 23 ° C. of a retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition aligned in a homogeneous arrangement. The polarizing element of Claim 1 or 2 whose difference (ne-no) with is 0.04-0.20.   The polarizing element according to any one of claims 1 to 3, wherein the positive C plate includes a retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition oriented in a homeotropic alignment.   A liquid crystal panel comprising the polarizing element according to claim 1 and a liquid crystal cell.   The liquid crystal panel according to claim 5, wherein the polarizing element according to claim 1 is disposed on a viewing side of the liquid crystal cell.   The liquid crystal panel according to claim 5 or 6, wherein a driving mode of the liquid crystal cell is an IPS mode, a VA mode, or an OCB mode.   A liquid crystal television comprising the liquid crystal panel according to claim 5. A liquid crystal display device comprising the liquid crystal panel according to claim 5.