JP2006323069A - Optically compensating sheet, method for manufacturing the same, and polarizing plate and liquid crystal display using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating type optically compensating sheet which contributes toward improving the frontal contrast of a liquid crystal display. <P>SOLUTION: The optically compensating sheet has a transparent support 11, an alignment layer 13 on the support and an optically anisotropic layer 12 formed on a surface of the alignment layer from a composition containing at least one polymerizable liquid crystal compound and at least one ultraviolet absorber which inhibits a polymerization reaction, wherein frontal retardation (Re) of the optically anisotropic layer is not 0, and a retardation value measured by making light having a wavelength λ nm incident from a direction tilted at +40° to a normal direction of the optically compensating sheet with an in-plane slow axis as an axis of tilt (axis of rotation) is substantially equal to a retardation value measured by making light having a wavelength λ nm incident from a direction tilted at -40° to a normal direction of the optically compensating sheet with an in-plane slow axis as an axis of tilt (axis of rotation). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical compensation sheet, a polarizing plate, and a liquid crystal display device, and more particularly to an optical compensation sheet, a polarizing plate, and a VA mode liquid crystal display device that are used in a vertical alignment (VA) mode liquid crystal display device. The present invention also relates to a method for producing an optical compensation sheet.

  CRT (Cathode Ray Tube) has been mainly used as a display device used for OA devices such as word processors, notebook personal computers, personal computer monitors, portable terminals, and televisions. In recent years, liquid crystal display devices have been widely used instead of CRTs because of their thinness, light weight, and low power consumption. The liquid crystal display device has a liquid crystal cell and a polarizing plate. The polarizing plate is composed of a protective film and a polarizing film, and is obtained by dyeing a polarizing film made of a polyvinyl alcohol film with iodine, stretching, and laminating both surfaces with a protective film. For example, in a transmissive liquid crystal display device, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation sheets may be disposed. On the other hand, in a reflective liquid crystal display device, a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate are arranged in this order. The liquid crystal cell includes a liquid crystal molecule, two substrates for encapsulating the liquid crystal molecule, and an electrode layer for applying a voltage to the liquid crystal molecule. A liquid crystal cell performs ON / OFF display depending on the alignment state of liquid crystal molecules, and can be applied to any of a transmission type, a reflection type, and a semi-transmission type, such as TN (Twisted Nematic), IPS (In-Plane Switching), Display modes such as OCB (Optically Compensatory Bend), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and STN (Super Twisted Nematic) are proposed. However, the color and contrast that can be displayed by a conventional liquid crystal display device vary depending on the angle at which the LCD is viewed. For this reason, the viewing angle characteristics of liquid crystal display devices have not yet exceeded the performance of CRT.

  In recent years, as an LCD method for improving the viewing angle characteristics, nematic liquid crystal molecules having negative dielectric anisotropy are used, and the major axis of the liquid crystal molecules is aligned in a direction substantially perpendicular to the substrate without applying a voltage. A vertical alignment nematic liquid crystal display device (hereinafter referred to as VA mode) in which this is driven by a thin film transistor has been proposed (see Patent Document 1). This VA mode not only has excellent display characteristics when viewed from the front, but also exhibits a wide viewing angle characteristic by applying a viewing angle compensation phase difference plate. In the VA mode, a wider viewing angle characteristic can be obtained by using a negative uniaxial retardation plate (negative c-plate) having an optical axis in a direction perpendicular to the film surface. It is also known that a wider viewing angle characteristic can be realized by using a uniaxially oriented retardation plate (positive a-plate) having a positive refractive index anisotropy having a retardation value of 50 nm ( Non-patent document 1).

  However, when the number of retardation plates is increased in this way, the production cost increases. In addition, since a large number of films are bonded together, it tends to cause not only a decrease in yield but also a deterioration in display quality due to a shift in the bonding angle. Furthermore, since a plurality of films are used, the thickness increases, which may be disadvantageous for thinning the display device.

  Further, a stretched film is usually used for positive a-plate, but when a simple longitudinally stretched film is used, the slow axis of a-plate is the film transport (MD) direction. However, in the VA mode viewing angle compensation, the slow axis of the a-plate must be orthogonal to the MD direction which is the absorption axis of the polarizing plate. Rises significantly. As a method for solving this, it is possible to use a so-called laterally stretched film that is stretched in a direction orthogonal to MD (TD direction). However, the transversely stretched film is apt to cause distortion of a slow axis called bowing, and the yield is high. The cost increases because it does not increase. Furthermore, since an adhesive layer is used for lamination of stretched films, the adhesive layer contracts due to temperature and humidity changes, and defects such as peeling and warping between films may occur. As a method for improving these, a method of producing a-plate by applying a rod-like liquid crystal is known (see Patent Document 2).

  Furthermore, in recent years, a method using a biaxial retardation plate in place of the combination of c-plate and a-plate has been proposed (Non-patent Document 2). By using a biaxial retardation plate, there is a merit that not only the contrast viewing angle but also the color can be improved. Usually, biaxial stretching used to produce a biaxial retardation plate is transverse stretching. Similarly, uniform axis control over the entire area of the film is difficult, and the yield does not increase, resulting in an increase in cost.

  Therefore, a method of producing a biaxial retardation plate without using stretching by a method of irradiating polarized light to a special cholesteric liquid crystal (Patent Document 3) or a method of irradiating polarized light to a special disc-shaped liquid crystal (Patent Document 4). Was proposed. By this method, various problems caused by stretching can be solved.

  However, the biaxiality of the optical compensation sheet by the biaxial retardation plate produced by the method of irradiating the liquid crystal coating with polarized light is not sufficient depending on the characteristics of the liquid crystal display device to be used. There were issues such as improvement.

Japanese Patent Laid-Open No. 2-176625 JP 2000-304930 A WO03 / 054111 A1 Japanese Patent Laid-Open No. 2002-6138 SID 97 DIGEST Pages 845-848 SID 2003 DIGEST, pages 1208-1211

  An object of the present invention is to provide an optical compensation sheet for use in a liquid crystal display element in which a liquid crystal cell is accurately optically compensated and can be accommodated even if the number of sheets to be bonded is reduced, that is, a thin layer can be manufactured. To provide an optical compensation sheet that is excellent in suitability and improved in biaxiality, and a method for producing the same. A further problem is to provide a polarizing plate and a liquid crystal display element, particularly a VA mode liquid crystal display element using the optical compensation sheet.

  Means for solving the above problems are as follows.

(1) Formed from a composition comprising a transparent support, an alignment layer on the support, and at least one polymerizable liquid crystal compound and at least one UV absorber for suppressing a polymerization reaction on the surface of the alignment layer And the optical retardation of the optical anisotropic layer is not 0,
Retardation value measured by injecting light of wavelength λ nm from a direction inclined + 40 ° with respect to the normal direction with the in-plane slow axis as the tilt axis (rotation axis), and the in-plane slow axis as the tilt axis An optical compensation sheet having substantially the same retardation value measured by making light having a wavelength λ nm incident from a direction inclined by −40 ° with respect to the normal direction as a rotation axis.
(2) The optical compensation sheet according to (1), wherein the polymerizable liquid crystal compound is a polymerizable rod-like liquid crystal compound, and the optically anisotropic layer is a layer formed by a polymerization reaction of a polymerizable group of the liquid crystal compound.
(3) The composition further comprises at least one chiral agent, and the optically anisotropic layer is a layer formed by polymerizing a polymerizable group of the polymerizable liquid crystal compound (1) or (2) Optical compensation sheet.
(4) The optical compensation sheet according to any one of (1) to (3), wherein the optically anisotropic layer is a layer formed by irradiating polarized light after cholesteric alignment of the rod-like liquid crystal compound molecules.
(5) The alignment layer is a layer formed from a composition containing at least one polymer having a polymerizable group in the side chain, or at least one monomer or oligomer having a polymerizable group. The optical compensation sheet according to any one of 4).
(6) The optical compensation sheet according to (5), wherein the polymer having a polymerizable group in the side chain is a modified polyvinyl alcohol having a polymerizable group.
(7) The optical compensation sheet according to (5) or (6), wherein the polymerizable group of the polymer is a polymerizable group containing an ethylene group or a cyclic ether group.
(8) The ultraviolet absorber is oriented in substantially the same direction as the rod-like liquid crystal compound in the uniaxially oriented rod-like liquid crystal compound, and the absorption exhibits dichroism in the ultraviolet region (1) to (7) Any one of the optical compensation sheets.

式中、Ａｒ¹及びＡｒ²はそれぞれ独立して、炭素数５〜１４の芳香環又は炭素数５〜１４の複素環を表し、それぞれ置換基を有していてもよい； (9) The optical compensation sheet according to any one of (1) to (8), wherein the ultraviolet absorber is an ultraviolet absorber represented by the following general formulas (I) to (III);

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and each may have a substituent;

式中、Ａｒ¹及びＡｒ²はそれぞれ独立して、炭素数５〜１４の芳香環又は炭素数５〜１４の複素環を表し、それぞれ置換基を有していてもよい；

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and each may have a substituent;

式中、Ａｒ¹及びＡｒ²はそれぞれ独立して、炭素数５〜１４の芳香環又は炭素数５〜１４の複素環を表し、それぞれ置換基を有していてもよく；Ｙは酸素原子、硫黄原子又は窒素原子を表し；Ｚは炭素原子又は窒素原子を表す。

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, each of which may have a substituent; Y represents an oxygen atom, Represents a sulfur atom or a nitrogen atom; Z represents a carbon atom or a nitrogen atom.

式中、Ａｒ¹は炭素数５〜１４の芳香環又は炭素数５〜１４の複素環を表し、置換基を有していてもよく；Ｗ¹及びＷ²はそれぞれ独立して、水素原子又は電子吸引基を表し、Ｖ¹は電子吸引基を表す。 (10) The optical compensation sheet according to any one of (1) to (8), wherein the ultraviolet absorber is an ultraviolet absorber represented by the following general formula (IV):

In the formula, Ar ¹ represents an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and may have a substituent; each of W ¹ and W ² independently represents a hydrogen atom or An electron withdrawing group is represented, and V ¹ represents an electron withdrawing group.

(11) The optical compensation sheet according to any one of (1) to (10), wherein the ultraviolet absorber is a compound having a polymerizable group.
(12) The optical compensation sheet according to any one of (1) to (11), wherein the transparent support contains a cellulose-based or cycloolefin-based polymer.
(13) A step of forming an alignment layer by applying a composition containing at least one polymer and / or at least one monomer on a transparent support, at least one liquid crystalline compound having a polymerizable group, at least one Applying a coating liquid of a liquid crystal composition containing an ultraviolet absorber and at least one chiral agent that suppresses the polymerization reaction of the liquid crystal compound onto the alignment layer, cholesteric alignment of the molecules of the liquid crystalline compound at an average tilt angle of less than 5 ° (1) The manufacturing method of the optical compensation sheet | seat which implements the process of irradiating polarized light, and the process of performing optical expression and superposition | polymerization simultaneously by irradiating polarized light.
(14) A polarizing plate comprising the optical compensation sheet according to any one of (1) to (12) and a polarizer.
(15) A liquid crystal display device having the optical compensation sheet of any one of (1) to (12) or the polarizing plate of (14).
(16) The liquid crystal display device according to (15), wherein the display mode is a VA mode.

  In the present invention, by adding an ultraviolet absorber that suppresses a polymerization reaction to the optically anisotropic layer, in particular, an ultraviolet absorber that suppresses a polymerization reaction that exhibits dichroism in liquid crystal alignment, the biaxiality of the optical compensation sheet Improves sex. By using the optical compensation sheet of the present invention, it is possible to optically compensate a liquid crystal cell with the same configuration as a conventional liquid crystal display element. Further, the liquid crystal display element having the optical compensation sheet of the present invention has not only display quality but also a viewing angle that is remarkably improved.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

  In this specification, Re, which is front retardation, and Rth, which is retardation in the thickness direction, is calculated based on the following. Re is measured with KOBRA 31PRN (manufactured by Oji Scientific Instruments Co., Ltd.) by making light of wavelength λ nm incident in the normal direction of the film. Rth changes the angle with respect to the normal direction of the film with the slow axis (determined by KOBRA 31PRN) in the Re plane as the tilt axis (rotation axis), and light of wavelength λ nm is incident from the tilted direction. KOBRA 31PRN calculates based on a plurality of measured retardation values. At this time, it is necessary to input an assumed value of average refractive index and a film thickness. KOBRA 31PRN calculates nx, ny, and nz in addition to Rth. The average refractive index of 1.48 is used for cellulose acetate, but values of polymer films for typical optical applications other than cellulose acetate include cycloolefin polymer (1.52), polycarbonate (1.59), poly Values such as methyl methacrylate (1.49) and polystyrene (1.59) can be used. As the average refractive index value of other existing polymer materials, the polymer handbook (John Wiley & Sons, Inc.) and the catalog values of polymer films can be used. In addition, in the case of a material whose average refractive index is unknown, it can be measured using an Abbe refractometer. In the present specification, λ indicates 590 ± 5 nm unless otherwise specified.

  In this specification, “substantially” for the angle means that the error from the exact angle is within a range of less than ± 10 °. Furthermore, the error from the exact angle is preferably less than 5 °, more preferably less than 3 °. With regard to retardation, “substantially” means that the retardation is within ± 10%. Furthermore, “Re is not 0” means that Re is 5 nm or more. In addition, the measurement wavelength of the refractive index indicates an arbitrary wavelength in the visible light region unless otherwise specified. In the present specification, “visible light” refers to light having a wavelength of 400 to 700 nm.

[Optical compensation sheet]
FIG. 1 is a schematic sectional view of an example of the optical compensation sheet of the present invention. The optical compensation sheet of the present invention has an optically anisotropic layer 12 on a transparent support 11. Between the transparent support 11 and the optically anisotropic layer 12, an alignment layer 13 that functions as an alignment layer for controlling the alignment of liquid crystalline molecules in the optically anisotropic layer 12 is disposed. The optically anisotropic layer 12 is a layer formed by irradiating a composition containing at least one polymerizable liquid crystal compound and at least one ultraviolet absorber that suppresses a polymerization reaction by irradiation with ionizing radiation. The optically anisotropic layer 12 has a front retardation (Re) which is not 0, and has a wavelength from a direction inclined by + 40 ° with respect to the normal direction of the optical compensation sheet with the in-plane slow axis as the tilt axis (rotation axis). Retardation value measured by making light of λnm incident, and light of wavelength λnm from a direction inclined by −40 ° with respect to the normal direction of the optical compensation sheet with the in-plane slow axis as the tilt axis (rotation axis) The retardation values measured by incidence are adjusted to be substantially equal. The optical compensation sheet of the present invention having such optical characteristics is a biaxial medium and can more accurately compensate a liquid crystal cell, particularly a VA mode liquid crystal cell.

[Polarizer]
2A to 2D are schematic sectional views of a polarizing plate having the optical compensation sheet of the present invention. In general, the polarizing plate can be prepared by dyeing a polarizing film made of a polyvinyl alcohol film with iodine and performing stretching to obtain the polarizing film 21, and laminating protective films 22 and 23 on both sides thereof. it can. Since the optical compensation sheet of the present invention has a support made of a polymer film or the like that supports the optically anisotropic layer, this support can be used as it is for at least one of the protective films 22 and 23. At this time, even if the optically anisotropic layer 12 is disposed on the polarizing layer 21 side (that is, the optically anisotropic layer 12 is closer to the polarizing layer 21 than the support 11), the optically anisotropic layer 12 is on the opposite side of the polarizing layer 21 ( That is, the optically anisotropic layer 12 may be disposed farther from the support 11 than the polarizing layer 21, but as shown in FIG. 2A, the optically anisotropic layer 12 includes the polarizing layer 21. It is preferable that it exists in the other side. Further, as shown in FIG. 2 (b), it is also possible to bond to the outside of one protective film 22 of the polarizing layer 21 via an adhesive or the like.

  2C and 2D are configuration examples of a polarizing plate in which another functional layer 24 is further arranged on the polarizing plate having the configuration shown in FIG. FIG. 2C is a configuration example in which another functional layer 24 is disposed on the protective film 23 disposed on the opposite side with the optical compensation sheet of the present invention and the polarizing layer 21 in between. ) Is a configuration example in which another functional layer 24 is arranged on the optical compensation sheet of the present invention. Examples of other functional layers are not particularly limited, and examples thereof include functional layers that impart various characteristics, such as λ / 4 layers, antireflection layers, and hard coat layers. These layers may be bonded together with, for example, an adhesive as a member such as a λ / 4 plate, an antireflection film, or a hard coat film. In the configuration example of FIG. Another functional layer 24 may be formed on the sheet (the optically anisotropic layer 12) and then bonded to the polarizing layer 21. Further, the protective film 23 itself on the side opposite to the optical compensation sheet of the present invention can be made into other functional films such as a λ / 4 plate, an antireflection film, and a hard coat film.

  When producing a polarizing plate by laminating a polarizing film and a protective film, a total of three films of a pair of protective film and polarizing film can be bonded together in a roll-to-roll manner. This roll-to-roll is a preferable method as a manufacturing process of a polarizing plate because it is difficult to cause dimensional change and curling of the polarizing plate as well as productivity, and can impart high mechanical stability.

[Liquid Crystal Display]
FIG. 3 shows an example of the liquid crystal display device of the present invention. The liquid crystal display device includes a liquid crystal cell 35 having a nematic liquid crystal sandwiched between upper and lower electrode substrates, and a pair of polarizing plates 36 and 37 disposed on both sides of the liquid crystal cell, and at least one of the polarizing plates. Uses the polarizing plate of the present invention shown in FIG. When using the polarizing plate of this invention, it arrange | positions so that an optically anisotropic layer may exist between a polarizing layer and the electrode substrate of a liquid crystal cell. Nematic liquid crystal molecules are controlled so as to be in a predetermined alignment state by providing an alignment layer applied on the electrode substrate and a rubbing process on the surface or a structure such as a rib.

  One or more light control films 34 such as a brightness enhancement film and a diffusion film may be provided below the liquid crystal cell sandwiched between the polarizing plates. Furthermore, the light control film has a reflection plate 32 and a light guide plate 33 for irradiating light emitted from the cold cathode tubes 31 to the front. Instead of a backlight unit comprising a cold cathode tube and a light guide plate, recently, a direct type backlight in which several cold cathode tubes are arranged under a liquid crystal cell, an LED backlight using an LED as a light source, or an organic EL Backlights that emit surface light using inorganic EL or the like are also used, but any of the optical films of the present invention is also effective in backlights.

  Further, although not shown in the figure, in the reflective liquid crystal display device, only one polarizing plate is required on the observation side, and a reflective film is provided on the back surface of the liquid crystal cell or on the inner surface of the lower substrate of the liquid crystal cell. . Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side. Further, a transflective type in which a transmissive portion and a reflective portion are provided in one pixel of the display device is also possible.

Next, materials used for manufacturing the optical compensation sheet of the present invention, manufacturing methods, and the like will be described in detail.
The optical compensation sheet of the present invention has an optically anisotropic layer, and the optically anisotropic layer contributes to increase the contrast viewing angle of the liquid crystal display device and eliminate image coloring of the liquid crystal display device. The optical compensation sheet of the present invention may include a support that supports the optically anisotropic layer. The support also serves as a protective film for the polarizing plate, or the optically anisotropic layer is a polarizing plate. By also serving as the protective film, the constituent members of the liquid crystal display device can be reduced. In other words, this aspect contributes to the thinning of the liquid crystal display device. Hereinafter, although this aspect demonstrates in detail about the material used for preparation, a preparation method, etc., this invention is not limited to this aspect. Other embodiments can also be produced with reference to the following description and conventionally known methods. However, the present invention is not limited to the aspect of the optical compensation sheet described below.

[Optically anisotropic layer]
The optical compensation sheet of the present invention has an optically anisotropic layer composed of a composition containing at least one polymerizable liquid crystal compound and at least one type of ultraviolet absorber that controls the polymerization reaction. The composition preferably contains a cholesteric liquid crystal, and more preferably contains a polymerizable cholesteric liquid crystal having a polymerizable group so that it can be cured by polymerization. Moreover, the said composition should just be able to form a cholesteric phase as a whole, ie, it is not essential to contain a cholesteric liquid crystal. In such a case, additives other than liquid crystals such as a polymerization initiator or a chiral agent contained in the composition contribute to the formation of the cholesteric phase. In addition, it is not essential that the liquid crystal molecule has a polymerizable group, a chiral agent or other additive may have a polymerizable group, and two or more polymerizable groups in one molecule. You may use the crosslinking agent which has group.

  In the present invention, as described above, the optically anisotropic layer has a front retardation (Re) which is not 0, and contributes to optical compensation of the liquid crystal cell. Of course, the optically anisotropic layer alone may have sufficient optical compensation ability, or may be an aspect satisfying the optical characteristics required for optical compensation in combination with other layers (for example, a support). The optically anisotropic layer is formed from a composition containing at least a liquid crystalline compound. In general, liquid crystal compounds can be classified into a rod-shaped type and a disk-shaped type based on their shapes. In addition, there are low and high molecular types, respectively. Polymer generally refers to a polymer having a degree of polymerization of 100 or more (Polymer Physics / Phase Transition Dynamics, Masao Doi, 2 pages, Iwanami Shoten, 1992). In the present invention, any liquid crystalline compound can be used, but a rod-like liquid crystalline compound is preferably used. You may use the 2 or more types of rod-shaped liquid crystalline compound or the mixture of a rod-shaped liquid crystalline compound and a disk shaped liquid crystalline compound. It is more preferable to use a rod-like liquid crystal compound having a polymerizable group because temperature change and humidity change can be reduced. In the case of a mixture, at least one of the liquid crystal molecules may have two or more polymerizable groups. Further preferred. The liquid crystalline compound may be a mixture of two or more kinds, and in that case, at least one preferably has two or more polymerizable groups.

  Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only the above low-molecular liquid crystalline compounds but also high-molecular liquid crystalline compounds can be used. The polymer liquid crystalline compound is a polymer compound obtained by polymerizing a rod-like liquid crystalline compound having a low molecular polymerizable group. The polymer liquid crystal compound also preferably has at least one polymerizable property, and more preferably has two or more polymerizable properties. The rod-like liquid crystal compound having a low-molecular polymerizable group that is particularly preferably used is a rod-like liquid crystal compound represented by the following general formula (V).

Formula (V): Q ¹ -L ¹ -A ¹ -L ³ -ML ⁴ -A ² -L ² -Q ²
Wherein, Q ¹ and Q ² each independently is a polymerizable group, L ^1, the L ^2, L ³ and L ⁴ each independently represent a single bond or a divalent linking group, L ³ and It is particularly preferable that at least one of L ⁴ is —O—CO—O—. A ¹ and A ² each independently represent a spacer group having 2 to 20 carbon atoms. M represents a mesogenic group.

Hereinafter, the rod-like liquid crystal compound having a polymerizable group represented by the general formula (V) will be described in more detail. In the formula, Q ¹ and Q ² are each independently a polymerizable group. The polymerization reaction of the polymerizable group is preferably addition polymerization (including ring-opening polymerization) or condensation polymerization. In other words, the polymerizable group is preferably a polymerizable group capable of addition polymerization reaction or condensation polymerization reaction. Examples of polymerizable groups are shown below.

Examples of the divalent linking group represented by L ¹ , L ² , L ³ and L ⁴ include —O—, —S—, —CO—, —NR ² —, —CO—O—, and —O—CO. —O—, —CO—NR ² —, —NR ² —CO—, —O—CO—, —O—CO—NR ² —, —NR ² —CO—O—, and NR ² —CO—NR ^2. A divalent linking group selected from the group consisting of-is preferred. R ² is an alkyl group having 1 to 7 carbon atoms or a hydrogen atom. In this case, it is preferable that at least one of L ³ and L ⁴ is —O—CO—O— (carbonate group). In formula (V), Q ¹ -L ¹ and Q ² -L ² -are preferably CH ₂ = CH-CO-O- and CH ₂ = C (CH ₃ ) -CO-O-, and CH ₂ = CH-CO-O- is most preferred.

A ¹ and A ² represent spacer groups having 2 to 20 carbon atoms. An aliphatic group having 2 to 12 carbon atoms is preferable, and an alkylene group is particularly preferable. The spacer group is preferably chain-like and may contain oxygen atoms or sulfur atoms that are not adjacent to each other. The spacer group may have a substituent and may be substituted with a halogen atom (fluorine, chlorine, bromine), a cyano group, a methyl group, or an ethyl group.

Examples of the mesogenic group represented by M include all known mesogenic groups. In particular, a group represented by the following general formula (VI) is preferable.
Formula (VI): - (- W 1 -L 5) n-W 2 -
In the formula, W ¹ and W ² each independently represent a divalent cycloaliphatic group, a divalent aromatic group or a divalent heterocyclic group, L ⁵ represents a single bond or a linking group, and Specific examples of the group include specific examples of the group represented by L ^{1 to} L ⁴ in the formula (V), —CH ₂ —O—, and —O—CH ₂ —. n represents 1, 2 or 3.

W ¹ and W ² include 1,4-cyclohexanediyl, 1,4-phenylene, pyrimidine-2,5-diyl, pyridine-2,5diyl, 1,3,4-thiadiazole-2,5-diyl, 1,3,4-oxadiazole-2,5-diyl, naphthalene-2,6-diyl, naphthalene-1,5-diyl, thiophene-2,5-diyl, pyridazine-3,6-diyl . In the case of 1,4-cyclohexanediyl, there are trans isomers and cis isomers, but either isomer may be used, and a mixture in any proportion may be used. More preferably, it is a trans form. W ¹ and W ² may each have a substituent. Examples of the substituent include a halogen atom (fluorine, chlorine, bromine, iodine), a cyano group, an alkyl group having 1 to 10 carbon atoms (methyl group, ethyl group, propyl group, etc.), and an alkoxy group having 1 to 10 carbon atoms. (Methoxy group, ethoxy group, etc.), C1-10 acyl group (formyl group, acetyl group, etc.), C1-10 alkoxycarbonyl group (methoxycarbonyl group, ethoxycarbonyl group, etc.), carbon atom Examples thereof include an acyloxy group having 1 to 10 (acetyloxy group, propionyloxy group, etc.), nitro group, trifluoromethyl group, difluoromethyl group and the like.

  Preferred examples of the basic skeleton of the mesogenic group represented by the general formula (VI) are shown below. These may be substituted with the above substituents.

  Examples of the compound represented by the general formula (V) are shown below, but the present invention is not limited thereto. The compound represented by the general formula (V) can be synthesized by the method described in JP-T-11-513019.

  As described above, the composition preferably contains a cholesteric liquid crystal having a polymerizable group. Moreover, a commercial item can also be used, for example, Palicolor LC242 (made by BASF Japan), Palicolor LC756 (made by BASF Japan), etc. can be used.

  The cholesteric pitch of the optically anisotropic layer is preferably 120 nm or less, and more preferably 100 nm or less. There is no particular limitation on the lower limit value. The thickness of the optically anisotropic layer is preferably 500 nm or more and 5 μm or less, and more preferably 700 nm or more and 4 μm or less. When the pitch is increased, light leakage in black display is increased, and as a result, contrast is deteriorated. On the other hand, when the thickness is increased, the thickness of the polarizing plate is increased and aging is deteriorated. On the other hand, if the thickness is less than the above range, the film thickness unevenness is easily noticeable, which is not preferable.

  Cholesteric pitch can be adjusted by the type and amount of chiral agent. In order to reduce the cholesteric pitch, it is necessary to select a chiral agent having as much helical twisting power as possible and increase the amount of the chiral agent added. In order to be able to add a large amount of the chiral agent, it is preferable that the chiral agent has at least one reactive group. As the reactive group, an ethylenically unsaturated group is preferable, and a (meth) acryl group is particularly preferable. Specifically, the chiral agent described in EP1388538 A1 page 16, 17 can be preferably used.

  The optically anisotropic layer has a retardation value measured by injecting light having a wavelength of λ nm from a direction inclined by + 40 ° with respect to the normal direction of the layer plane with the in-plane slow axis as the tilt axis (rotation axis). The retardation values measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the normal direction of the layer plane with the in-plane slow axis as the tilt axis (rotation axis) are substantially equal. It has the optical characteristics. In the case of using a liquid crystalline compound having a polymerizable group, in order to develop biaxiality, a dichroic liquid crystalline polymerization initiator is used to form a cholesteric alignment or a hybrid cholesteric alignment in which the tilt angle gradually changes in the thickness direction. Can be used to select a method of distortion by irradiation with polarized light (WO03 / 054111 A1).

  In any aspect of the present invention, the optical retardation sheet as a whole has a front retardation Re of 70 nm or less, and an in-plane slow axis as an inclined axis (rotation axis) with respect to the normal direction of the optical compensation sheet. It is preferable that the retardation Re (40) and Re (−40) measured from a direction inclined by 40 ° is 30 to 150 nm.

  When two or more optically anisotropic layers made of a liquid crystalline compound are laminated, the combination of the liquid crystalline compounds is not particularly limited, and even if it is a laminate of all layers made of a discotic liquid crystalline compound, it is all rod-like. Even if it is a laminated body of the layer which consists of a liquid crystalline compound, the laminated body of the layer which consists of a layer which consists of a discotic liquid crystalline compound, and a rod-like liquid crystalline compound may be sufficient. The combination of the alignment states of the layers is not particularly limited, and optically anisotropic layers having the same alignment state may be stacked, or optically anisotropic layers having different alignment states may be stacked.

  The optically anisotropic layer is preferably formed by applying a coating liquid containing a liquid crystalline compound and the following polymerization initiator and other additives onto the alignment layer. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

[Fixation of alignment state of liquid crystalline compounds]
The aligned liquid crystalline compound is preferably fixed while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is more preferable. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. The irradiation energy is preferably ^{20mJ / cm 2 ~10J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

[Optical alignment by polarized irradiation]
The optically anisotropic layer of the present invention can generate in-plane retardation by photo-alignment by polarized light irradiation. This polarized light irradiation may be performed at the same time as the photopolymerization process in the above-described orientation fixation, or may be further fixed by non-polarized light irradiation after first polarized light irradiation, or may be fixed first by non-polarized light irradiation. Then, photo-alignment may be performed by irradiation with polarized light. In order to obtain a large retardation, it is preferable to irradiate polarized light alone or first. The polarized light irradiation is preferably performed in an inert gas atmosphere having an oxygen concentration of 0.5% or less. For polarized light irradiation, ultraviolet polarized light irradiation is preferable, particularly polarized light irradiation having a peak at 365 ± 10 nm is preferable, and polarized light irradiation having a peak at 365 ± 5 nm is more preferable. The irradiation energy is preferably ^{20mJ / cm 2 ~10J / cm 2} , further preferably 100 to 800 mJ / cm ^2. The illuminance is preferably 20 to 1000 mW / cm ^2, more preferably 50 to 500 mW / cm ^2, further preferably 100 to 350 mW / cm ^2. Although there is no restriction | limiting in particular about the kind of liquid crystalline compound hardened | cured by polarized light irradiation, The liquid crystalline compound which has an ethylenically unsaturated group as a reactive group is preferable.

[Horizontal alignment agent]
By containing at least one compound represented by the following general formulas (1) to (3) in the composition for forming the optically anisotropic layer, the molecules of the liquid crystalline compound are substantially horizontally aligned. be able to. In the present invention, “horizontal alignment” means that in the case of a rod-like liquid crystal, the molecular long axis is parallel to the horizontal plane of the transparent support. In the case of a disc-like liquid crystal, the disc surface of the core of the disc-like liquid crystal compound. And the horizontal plane of the transparent support is parallel, but it is not required to be strictly parallel, and in this specification, an inclination angle with the horizontal plane is less than 10 degrees. To do. The inclination angle is preferably 0 to 5 degrees, more preferably 0 to 3 degrees, further preferably 0 to 2 degrees, and most preferably 0 to 1 degree.
Hereinafter, the following general formulas (VII) to (IX) will be described in order.

In the formula, R ¹ , R ² and R ³ each independently represent a hydrogen atom or a substituent, and X ¹ , X ² and X ^{3 each} represent a single bond or a divalent linking group. The substituent represented by each of R ^{1 to} R ³ is preferably a substituted or unsubstituted alkyl group (more preferably an unsubstituted alkyl group or a fluorine-substituted alkyl group), an aryl group (particularly a fluorine-substituted alkyl). An aryl group having a group is preferred), a substituted or unsubstituted amino group, an alkoxy group, an alkylthio group, and a halogen atom. The divalent linking groups represented by X ¹ , X ² and X ³ are each an alkylene group, an alkenylene group, a divalent aromatic group, a divalent heterocyclic residue, —CO—, —NR ^a — ( R ^a is ^a divalent linking group selected from the group consisting of an alkyl group having 1 to 5 carbon atoms or a hydrogen atom), —O—, —S—, —SO—, —SO ₂ —, and combinations thereof. Preferably there is. The divalent linking group is selected from the group consisting of an alkylene group, a phenylene group, —CO—, —NR ^a —, —O—, —S—, and —SO ₂ —. It is more preferable that the divalent linking group is a combination of at least two groups. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The number of carbon atoms of the divalent aromatic group is preferably 6-10.

In the formula, R represents a substituent, and m represents an integer of 0 to 5. When m represents an integer greater than or equal to 2, several R may be same or different. Preferred substituents for R are the same as those listed as preferred ranges for the substituents represented by R ¹ , R ² and R ³ . m preferably represents an integer of 1 to 3, particularly preferably 2 or 3.

In the formula, R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a hydrogen atom or a substituent. The substituents represented by R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are each preferably the substituents represented by R ¹ , R ² and R ³ in the general formula (VII). It is listed as a thing. As the horizontal alignment agent used in the present invention, the compounds described in JP-A-2005-99248 can be used, and the synthesis method of these compounds is also described in the specification.

  The addition amount of the compounds represented by the general formulas (VII) to (IX) is preferably 0.01 to 20% by mass, more preferably 0.01 to 10% by mass based on the mass of the liquid crystal compound. 02-1 mass% is especially preferable. In addition, the compounds represented by the general formulas (VII) to (IX) may be used alone or in combination of two or more.

[Ultraviolet absorber]
In the present invention, the “ultraviolet absorber that suppresses the polymerization reaction” means that by adding the ultraviolet absorber, the polymerization reaction rate of the polymerizable liquid crystal compound to be used in combination can be delayed as compared with the case where it is not added. It means an ultraviolet absorber that can be used. By suppressing the polymerization reaction of the liquid crystal compound, for example, the distortion of the cholesteric layer of the optically anisotropic layer due to the irradiation of polarized light of ionizing radiation such as ultraviolet rays is increased, and the expression of biaxiality is enhanced. Specifically, the addition amount is not particularly limited, but is preferably 10% or less, more preferably 3% or less, with respect to the total solid concentration of the composition constituting the optically anisotropic layer.

  Confirmation of inhibition of the polymerization reaction is carried out by evaluating the conversion rate of the polymerization reaction depending on whether or not the ultraviolet absorber is added. Various known methods can be employed for measuring the conversion rate. For example, a method using a change caused by a polymerization reaction such as an infrared absorption spectrum or a Raman spectrum can be employed. As an index, an ultraviolet absorber that lowers the conversion rate by 3% or more by addition is preferable, and an ultraviolet absorber that decreases 5% or more is more preferable.

  The ultraviolet absorber that suppresses the polymerization reaction is not particularly limited as long as the polymerization reaction of the polymerizable liquid crystal compound can be suppressed, but an ultraviolet absorber that exhibits dichroism in the ultraviolet region is preferable. Further, an ultraviolet absorber in which an ethylene group having an electron withdrawing group is linked to an aromatic ring or a heterocyclic ring is also preferable.

  In the present invention, the ultraviolet absorber having dichroism is an absorption at 180 to 420 nm, and when a layer showing a uniaxially oriented liquid crystal phase mixed with a rod-like liquid crystalline compound is formed, the polarization of a specific polarization plane It means a material having dichroism in the property of absorbing water. The dichroism of the ultraviolet absorber is a parallel structure in which an ultraviolet absorber is added to an arbitrary rod-like liquid crystalline compound in a cell composed of two glass substrates having alignment layers arranged in parallel in the rubbing direction. In the cell, it can be confirmed that the ratio of the absorption peak of the ultraviolet absorbent to the polarized light parallel to the rubbing direction and the polarized light orthogonal to the rubbing direction is 75% or less or 125% or more. In addition, when the ultraviolet absorber can be uniaxially oriented alone, the ultraviolet absorber is applied and oriented on a transparent substrate such as quartz having a rubbing-oriented alignment layer, and polarized light parallel to the rubbing direction. It can also be confirmed that the ratio of the absorption peak of the ultraviolet absorber to the orthogonally polarized light is 75% or less or 125% or more. As an absorption peak wavelength, 300-400 nm is preferable and 350-380 nm is especially preferable.

  Hereinafter, the compounds represented by the general formulas (I) to (IV) which are preferable ultraviolet absorbers will be described in detail.

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and each may have a substituent. Ar ¹ and Ar ² are each preferably a benzene ring or a naphthalene ring, and particularly preferably a benzene ring. When Ar ¹ and Ar ² each have a substituent, the substituent is preferably an alkyl group, an alkoxy group, an alkenyl group, an alkenyloxy group or an aryl group, and particularly preferably an alkyl group or an alkoxy group. In addition, these substituents may have a polymerizable group via a single bond or a divalent linking group. The divalent linking group is preferably an ether group or a carbonyloxy group. The polymerizable group is as described for the polymerizable group Q ¹ .

  Specific examples of the compound represented by formula (I) are shown below. However, the present invention is not limited to this.

式中、Ａｒ¹及びＡｒ²はそれぞれ独立して、炭素数５〜１４の芳香環、あるいは炭素数５〜１４の複素環を示し、それぞれ置換基を有していてもよい。Ａｒ¹及びＡｒ²、ならびにその置換基に関してはそれぞれ、前記一般式（Ｉ）の説明における記述の通りである。

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and each may have a substituent. Ar ¹ and Ar ² and their substituents are the same as described in the description of the general formula (I).

  Specific examples of the compound represented by the general formula (II) are shown below. However, the present invention is not limited to this.

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and each may have a substituent. Ar ¹ and Ar ² are each preferably a benzene ring, thiophene ring or naphthalene ring, particularly preferably a benzene ring or naphthalene ring. When Ar ¹ and Ar ² each have a substituent, the substituent is preferably an alkyl group, an alkoxy group, an alkenyl group, an alkenyloxy group, an alkyloxycarbonyl group, an alkyloxysulfonyl group or an aryl group, and an alkyl group or an alkoxy group Is particularly preferred. In addition, these substituents may have a polymerizable group via a single bond or a divalent linking group. The divalent linking group is preferably an ether group or a carbonyloxy group. The polymerizable group is as described for the polymerizable group Q ¹ .
Y represents an oxygen atom, a sulfur atom or a nitrogen atom, and is preferably a sulfur atom. When Y represents a nitrogen atom, a hydrogen atom, an alkyl group, an aryl group, or an acyl group is bonded to the nitrogen atom. Z represents a carbon atom or a nitrogen atom, and a carbon atom is preferable. When Z represents a carbon atom, a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group or a halogen atom is bonded to the carbon atom.

  Specific examples of the compound represented by the general formula (III) are shown below. However, the present invention is not limited to this.

In the formula, Ar ¹ independently represents an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and each may have a substituent. Ar ¹ is preferably a benzene ring, naphthalene ring or thiophene ring, particularly preferably a benzene ring or naphthalene ring. W ¹ and W ² each represent a hydrogen atom or an electron withdrawing group, and V ¹ represents an electron withdrawing group.

  The electron withdrawing group refers to a substituent having Hammett's substituent constant σp> 0. Hammett substituent constants are described in detail in C. Hansch, A. Leo. And R.W. Taft, Chemical Review, 1991, 91, pp. 165-195.

When W ¹ and W ² each represent an electron withdrawing group, W ¹ and W ² are each preferably a nitrile group, a nitro group, an alkyloxycarbonyl group or an alkyloxysulfonyl group. The electron withdrawing group may have a polymerizable group through a single bond or a divalent linking group. The divalent linking group is preferably an ether group or a carbonyloxy group. The polymerizable group is as described for the polymerizable group Q ¹ . The electron withdrawing group represented by V ¹ is preferably a nitrile group, a nitro group, an alkyloxycarbonyl group or an alkyloxysulfonyl group. The electron withdrawing group may have a polymerizable group through a single bond or a divalent linking group. The divalent linking group is preferably an ether group or a carbonyloxy group. The polymerizable group is as described for the polymerizable group Q ¹ .

  Specific examples of the compound represented by the general formula (IV) are shown below. However, the present invention is not limited to this.

[Alignment layer]
In order to align the liquid crystalline compound, a predetermined polymer layer is preferably used as the alignment layer. In general, the alignment layer is formed by rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroup, or an organic compound (for example, ω-tricco) by the Langmuir-Blodgett method (LB film). Acid, dioctadecyldimethylammonium chloride, methyl stearylate, etc.). Furthermore, an alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. The rubbing process is carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.

  In the present invention, a polymer layer formed by applying and drying a solution is preferably used as the alignment layer. A polymer is preferably used for forming the alignment layer. The type of polymer that can be used can be determined according to the orientation (particularly the average tilt angle) of the liquid crystal compound. For example, in order to align the liquid crystalline compound horizontally, a polymer (ordinary alignment polymer) that does not decrease the surface energy of the alignment film is used. Specific types of polymers are described in various documents about liquid crystal cells or optical compensation sheets. For example, polyvinyl alcohol or modified polyvinyl alcohol, a copolymer with polyacrylic acid or polyacrylate, polyvinyl pyrrolidone, cellulose, or modified cellulose are preferably used. Any of the alignment films preferably has a polymerizable group for the purpose of improving the adhesion between the liquid crystal compound and the transparent support. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group. It is more preferable to use an alignment film that forms a chemical bond with a liquid crystal compound at the interface. Such an alignment film is described in JP-A-9-152509, and acid chloride or Karenz MOI (manufactured by Showa Denko KK). The modified polyvinyl alcohol in which an acrylic group is introduced into the side chain by using The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

  The optically anisotropic layer can be transferred by aligning the liquid crystalline compound on the temporary alignment layer, fixing the alignment, and then using an adhesive on the transparent support. It is preferable to form a functional film directly without transfer.

  Each of the optical anisotropic layer and the alignment layer is formed by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method or an extrusion coating method (US Pat. No. 2,681,294). Can be formed by coating. Two or more layers may be applied simultaneously. The method of simultaneous application is described in US Pat. Nos. 2,761,791, 2,941,898, 3,508,947, and 3,526,528 and Yuji Harasaki, Coating Engineering, page 253, Asakura Shoten (1973).

[Transparent support]
As the transparent support for the optically anisotropic layer, it is preferable to use a polymer film having a light transmittance of 80% or more. The thickness of the transparent support is preferably 10 to 500 μm, more preferably 20 to 200 μm, and most preferably 35 to 110 μm.

  The glass transition temperature (Tg) of the transparent support of the present invention is appropriately determined according to the purpose of use. The glass transition temperature of the resin is preferably 70 ° C. or higher, more preferably 75 ° C. to 200 ° C., and particularly preferably 80 ° C. to 180 ° C. When a resin in this range is employed, heat resistance and molding processability are highly balanced, which is preferable.

  The Re of the transparent support is preferably adjusted to a range of −200 to 100 nm, and Rth is preferably adjusted to a range of −100 to 100 nm. Re is more preferably −50 to 30 nm, and most preferably −30 to 20 nm.

  Examples of the polymer constituting the transparent support include cellulose ester (eg, cellulose acetate, cellulose propionate, cellulose butyrate), polyolefin (eg, norbornene-based polymer), poly (meth) acrylic acid ester (eg, poly Methyl methacrylate), polycarbonate, polyester and polysulfone. Commercially available polymers (for norbornene polymers, Arton (manufactured by JSR), Zeonore (manufactured by Nippon Zeon), etc.) may be used.

  In particular, when used as a protective film for a polarizing plate, a cellulose ester is preferable, and a lower fatty acid ester of cellulose is more preferable. Lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. Of the lower fatty acid esters of cellulose, cellulose acetate is most preferred. The acyl group substitution degree of the cellulose ester is preferably 2.50 to 3.00, more preferably 2.75 to 2.95, and most preferably 2.80 to 2.90.

  The viscosity average polymerization degree (DP) of the cellulose ester is preferably 250 or more, and more preferably 290 or more. In addition, the cellulose ester preferably has a narrow molecular weight distribution of Mm / Mn (Mm is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The value of Mm / Mn is preferably 1.0 to 5.0, more preferably 1.3 to 3.0, and most preferably 1.4 to 2.0.

  In the cellulose ester, the hydroxyl groups at the 2-position, 3-position and 6-position of cellulose are not evenly substituted but the degree of substitution at the 6-position tends to be small. In the present invention, the 6-position substitution degree of the cellulose ester is preferably about the same as or higher than the 2-position and 3-position. The ratio of the 6-position substitution degree to the total of the 2-position, 3-position and 6-position substitution degrees is preferably 30 to 40%. The ratio of the 6-position substitution degree is preferably 31% or more, particularly preferably 32% or more. The substitution degree at the 6-position is preferably 0.88 or more. The 6-position of cellulose may be substituted with an acyl group having 3 or more carbon atoms (eg, propionyl, butyryl, valeroyl, benzoyl, acryloyl) in addition to acetyl. The degree of substitution at each position can be measured by NMR. Cellulose esters having a high degree of substitution at the 6-position are described in Synthesis Example 1 described in Paragraph Nos. 0043 to 0044, Synthesis Example 2 described in Paragraph Nos. 0048 to 0049, and Paragraph Nos. 0051 to 0052. It can synthesize | combine with reference to the synthesis example 3 of these.

  A plasticizer can be added to the cellulose ester film in order to improve mechanical properties or increase the drying speed. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The addition amount of the plasticizer is preferably 0.1 to 25% by weight of the amount of cellulose ester, more preferably 1 to 20% by weight, and most preferably 3 to 15% by weight.

  A degradation inhibitor (eg, antioxidant, peroxide decomposer, radical inhibitor, metal deactivator, acid scavenger, amine) may be added to the cellulose ester film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by weight of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by weight. When the addition amount is less than 0.01% by weight, the effect of the deterioration preventing agent is hardly recognized. When the added amount exceeds 1% by weight, bleed-out (bleeding) of the deterioration preventing agent to the film surface may be observed. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA). Furthermore, a very small amount of dye may be added to prevent light piping. From the viewpoint of transmittance, it is preferable to adjust the type and amount so that the transmittance of light having a wavelength of 420 nm is 50% or more. The added amount of the dye is preferably 0.01 ppm to 1 ppm.

  In order to control the Re retardation value and the Rth retardation value, a retardation control agent can be added to the cellulose ester film. The retardation control agent is preferably used in the range of 0.01 to 20 parts by mass, more preferably 0.05 to 15 parts by mass, with respect to 100 parts by mass of the cellulose ester. Most preferably, it is used in the range of 1 to 10 parts by mass. Two or more retardation control agents may be used in combination. The retardation control agent is described in pamphlets of WO01 / 88574 and WO00 / 2619, and JP-A 2000-1111914 and 2000-275434.

  The cellulose ester film can be produced by a solvent cast method using a solution containing cellulose ester and other components as a dope. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 10 to 40% by weight. The solid content is more preferably 18 to 35% by weight. Two or more dopes can be cast. The surface of the drum or band is preferably finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.

  The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. Then, the method can be employed in which the obtained film is peeled off from the drum or band and further dried with high-temperature air at different temperatures of 100 to 160 ° C. to evaporate the residual solvent (described in Japanese Patent Publication No. 5-17844). . According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting. When casting a plurality of cellulose ester solutions, a solution is prepared by casting a solution containing cellulose ester from a plurality of casting openings provided at intervals in the traveling direction of the support, and laminating them. (Japanese Patent Laid-Open Nos. 61-158414, 1-122419, and 11-198285). A film can also be produced by casting a cellulose ester solution from two casting ports (Japanese Patent Publication Nos. 60-27562, 61-94724, 61-947245, 61-104413, No. 61-158413 and JP-A-6-134933). Employs a method of casting a cellulose ester film (described in JP-A-56-162617) by wrapping a flow of a high-viscosity cellulose ester solution with a low-viscosity cellulose ester solution and simultaneously extruding the high-viscosity and low-viscosity cellulose ester solutions. May be.

  The retardation of the cellulose ester film can be further adjusted by a stretching treatment. The draw ratio is preferably in the range of 3 to 100%. Tenter stretching is preferred. In order to control the slow axis with high accuracy, it is preferable to make the difference between the left and right tenter clip speeds and the separation timing as small as possible. The stretching process is described on page 37, line 8 to page 38, line 8 of the pamphlet of WO 01/88574.

  The cellulose ester film can be subjected to a surface treatment. Examples of the surface treatment include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose ester film in the surface treatment is preferably Tg (glass transition temperature) or lower, specifically 150 ° C. or lower.

  The thickness of the cellulose ester film can be adjusted by lip flow rate and line speed, or stretching or compression when it is produced by film formation. Since the moisture permeability varies depending on the main material to be used, it is possible to adjust the thickness to a preferable moisture permeability range as a protective film for the polarizing plate. Moreover, the free volume of the said cellulose-ester film can be adjusted with drying temperature and time, when producing by film forming. Also in this case, since the moisture permeability varies depending on the main material used, it is possible to make the moisture permeability range preferable as a protective film by adjusting the free volume. The hydrophilicity / hydrophobicity of the cellulose ester film can be adjusted by an additive. Moisture permeability is increased by adding a hydrophilic additive in the free volume, and conversely, moisture permeability can be lowered by adding a hydrophobic additive. Thus, by adjusting the moisture permeability of the cellulose ester film by various methods, it is possible to obtain a range of moisture permeability preferable as a protective film for the polarizing plate, and the support of the optically anisotropic layer is protected for the polarizing plate. A polarizing plate that can also serve as a film and has an optical compensation capability can be manufactured at low cost with high productivity.

[Polarizer]
The polarizing plate used for the liquid crystal display device of the present invention comprises a polarizing film and a pair of protective films that sandwich the polarizing film. Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The kind of protective film is not particularly limited, and cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate, polycarbonate, polyolefin, polystyrene, polyester, and the like can be used. The transparent protective film is usually supplied in a roll form, and it is preferable that the transparent protective film is continuously bonded to the long polarizing film so that the longitudinal directions thereof coincide. Here, the orientation axis (slow axis) of the protective film may be any direction. Further, the angle between the slow axis (alignment axis) of the protective film and the absorption axis (stretching axis) of the polarizing film is not particularly limited, and can be appropriately set according to the purpose of the polarizing plate.

The polarizing film and the protective film may be bonded together with an aqueous adhesive. The adhesive solvent in the water-based adhesive is dried by diffusing in the protective film. The higher the moisture permeability of the protective film, the faster the drying and the higher the productivity. However, if the protective film is too high, the moisture will enter the polarizing film due to the usage environment (high humidity) of the liquid crystal display device. The performance drops. The moisture permeability of the optical compensation sheet is determined by the thickness, free volume, hydrophilicity / hydrophobicity, etc. of the polymer film (and polymerizable liquid crystal compound). The moisture permeability of the protective film for the polarizing plate is preferably in the range of 100 to 1000 (g / m ² ) / 24 hrs, and more preferably in the range of 300 to 700 (g / m ² ) / 24 hrs.

  In the present invention, for the purpose of reducing the thickness, one of the protective films of the polarizing film may also serve as the support for the optically anisotropic layer, or the optically anisotropic layer itself. The optically anisotropic layer and the polarizing film are preferably subjected to a fixing treatment from the viewpoint of preventing displacement of the optical axis and preventing entry of foreign matters such as dust. An appropriate method such as an adhesive method through a transparent adhesive layer can be applied to the fixed lamination. There is no particular limitation on the type of the adhesive and the like, and from the viewpoint of preventing changes in the optical properties of the constituent members, those that do not require a high-temperature process during curing or drying are preferable, and a long-time curing process is preferable. And those that do not require drying time. From such a viewpoint, a hydrophilic polymer adhesive or a pressure-sensitive adhesive layer is preferably used.

  Appropriate functional layers such as a protective film for various purposes such as water resistance according to the above protective film, an antireflection layer and / or an antiglare treatment layer for the purpose of preventing surface reflection, etc. on one or both sides of the polarizing film You may use the polarizing plate which formed. The antireflection layer can be suitably formed, for example, as a light interference film such as a fluorine polymer coating layer or a multilayer metal vapor deposition film. The antiglare layer is also formed by an appropriate method that diffuses the surface reflected light, for example, by providing a fine uneven structure on the surface by an appropriate method such as a resin coating layer containing fine particles, embossing, sandblasting or etching. can do.

  Examples of the fine particles include inorganic materials such as silica, calcium oxide, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide having an average particle diameter of 0.5 to 20 μm. One kind or two or more kinds of fine particles, cross-linked or non-cross-linked organic fine particles made of a suitable polymer such as polymethyl methacrylate and polyureta can be used. The above-mentioned adhesive layer or pressure-sensitive adhesive layer may contain such fine particles and exhibit light diffusibility.

  The optical properties and durability (storability in the short term and long term) of the polarizing plate comprising the protective film, the polarizing film and the transparent support relating to the present invention are commercially available super high contrast products (for example, manufactured by Sanritz Corporation). HLC2-5618 etc.) is preferable. Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization √ ({(Tp−Tc) / (Tp + Tc)} ≧ 0.9995 (where Tp is parallel transmittance and Tc is orthogonal transmittance) ), And the change rate of the light transmittance before and after being left for 500 hours in an atmosphere of 60 ° C. and humidity of 90% RH for 500 hours and 80 ° C. in a dry atmosphere is 3% or less based on the absolute value, Further, it is preferably 1% or less, and the rate of change in polarization degree is preferably 1% or less, more preferably 0.1% or less based on the absolute value.

  The display mode of the liquid crystal display device used in the present invention is not particularly limited, but the VA mode is preferably used. Note that the liquid crystal display device used in the present invention is effective not only in the display mode but also in an aspect applied to the STN mode, the TN mode, and the OCB mode.

[VA mode liquid crystal cell]
In the present invention, the liquid crystal cell is preferably in a vertically aligned mode (VA mode). The VA mode liquid crystal cell is formed by sealing liquid crystal molecules having negative dielectric anisotropy between upper and lower substrates whose opposite surfaces are rubbed. For example, by using liquid crystal molecules having Δn = 0.0813 and Δε = −4.6, a director indicating the alignment direction of the liquid crystal molecules, that is, a liquid crystal cell having a so-called tilt angle of about 89 ° can be manufactured. At this time, the thickness d of the liquid crystal layer can be about 3.5 μm. The brightness at the time of white display changes depending on the magnitude of the product Δn · d of the thickness d (nm) of the liquid crystal layer and the refractive index anisotropy Δn. In order to obtain the maximum brightness, the thickness d of the liquid crystal layer is preferably in the range of 2 to 5 μm (2000 to 5000 nm), and Δn is in the range of 0.060 to 0.085.

  Transparent electrodes are formed inside the upper and lower substrates of the liquid crystal cell, but in a non-driving state where no driving voltage is applied to the electrodes, the liquid crystal molecules in the liquid crystal layer are aligned approximately perpendicular to the substrate surface, resulting in liquid crystals The polarization state of the light passing through the panel hardly changes. Since the absorption axis of the upper polarizing plate 37 of the liquid crystal cell and the absorption axis of the lower polarizing plate 36 are substantially orthogonal, light does not pass through the polarizing plate. In other words, in the VA mode liquid crystal display device, an ideal black display can be realized in the non-driven state. On the other hand, in the driving state, the liquid crystal molecules are inclined in a direction parallel to the substrate surface, and the light passing through the liquid crystal panel changes the polarization state by the inclined liquid crystal molecules and passes through the polarizing plate.

  Up to this point, since an electric field is applied between the upper and lower substrates, an example using a liquid crystal material having a negative dielectric anisotropy in which liquid crystal molecules respond perpendicularly to the electric field direction has been shown. In the case where the liquid crystal material is disposed on the substrate and an electric field is applied in a lateral direction parallel to the substrate surface, a liquid crystal material having a positive dielectric anisotropy can be used.

  The characteristics of the VA mode are high-speed response and high contrast. However, there is a problem that the contrast is high in the front but decreases in the oblique direction. Since the liquid crystal molecules are aligned perpendicular to the substrate surface during black display, when viewed from the front, there is almost no birefringence of the liquid crystal molecules, so the transmittance is low and high contrast can be obtained. However, when observed obliquely, birefringence occurs in the liquid crystalline molecules. Furthermore, the crossing angle of the upper and lower polarizing plate absorption axes is 90 ° perpendicular to the front, but is greater than 90 ° when viewed from an oblique direction. Due to these two factors, leakage light tends to occur in the oblique direction, and the contrast tends to decrease. In the present invention, in order to solve this problem, at least one optically anisotropic layer is provided on a transparent support having predetermined optical characteristics.

  In the VA mode, liquid crystal molecules are tilted during white display, but the birefringence of the liquid crystal molecules when viewed from an oblique direction is different between the tilt direction and the opposite direction, resulting in differences in luminance and color tone. . In order to solve this, the liquid crystal cell is preferably multi-domain. Multi-domain refers to a structure in which a plurality of regions having different alignment states are formed in one pixel. For example, in a multi-domain VA mode liquid crystal cell, a plurality of regions in which tilt angles of liquid crystal molecules are different from each other when an electric field is applied exist in one pixel. In a multi-domain VA mode liquid crystal cell, the tilt angle of liquid crystal molecules due to application of an electric field can be averaged for each pixel, whereby the viewing angle characteristics can be averaged. Dividing the orientation within one pixel can be achieved by providing a slit in the electrode, providing a protrusion, changing the direction of the electric field, or biasing the electric field density. In order to obtain a uniform viewing angle in all directions, the number of divisions may be increased. However, since the transmittance during white display is reduced, four divisions are preferable.

  In a VA mode liquid crystal display device, the addition of a chiral material generally used in a Twisted Nematic mode (TN mode) liquid crystal display device is rarely used to degrade the dynamic response characteristics. Sometimes added to reduce. At the boundary of the alignment division, the liquid crystal molecules are difficult to respond. For this reason, in normally black display, since black display is maintained, a reduction in luminance becomes a problem. Adding a chiral agent to the liquid crystal material contributes to reducing the boundary region.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

(Preparation of transparent support S-1)
A commercial cellulose acetate film, Fujitac TD80UF (Fuji Photo Film Co., Ltd., Re = 3 nm, Rth = 50 nm) was used as the transparent support S-1.

(Preparation of coating liquid AL-1 for alignment layer)
The following composition was prepared, filtered through a polypropylene filter having a pore size of 30 μm, and used as an alignment layer coating liquid AL-1. As the modified polyvinyl alcohol, one disclosed in JP-A-9-152509 was used.
───────────────────────────────────
Coating liquid composition for alignment layer (%)
───────────────────────────────────
Modified polyvinyl alcohol AL-1-1 4.01
Water 72.89
Methanol 22.83
Glutaraldehyde (crosslinking agent) 0.20
Citric acid 0.008
Citric acid monoethyl ester 0.029
Citric acid diethyl ester 0.027
Citric acid triethyl ester 0.006
───────────────────────────────────

(Preparation of coating liquid LC-1 for optically anisotropic layer)
After the following composition was prepared, it was filtered through a polypropylene filter having a pore size of 0.2 μm and used as a coating liquid LC-1 for an optically anisotropic layer.

──────────────────────────────────――
Coating composition for optically anisotropic layer (%)
──────────────────────────────────――
Bar-shaped liquid crystal 28.37
(Paliocolor LC242, manufactured by BASF Japan)
Chiral agent 3.30
(Paliocolor LC756, manufactured by BASF Japan)
Photopolymerization initiator (LC-1-1) 1.32
Additive (LC-1-2) 0.01
Methyl ethyl ketone 67.00
─────────────────────────────────────

LC-1-1:
It was synthesized by the method described in EP1388538A1.
LC-1-2:
The compound was synthesized according to the method described in Tetrahedron Lett., Vol. 43, page 6793 (2002).

(Preparation of coating liquid LC-2 for optically anisotropic layer)
After the following composition was prepared, it was filtered through a polypropylene filter having a pore size of 0.2 μm and used as a coating liquid LC-1 for an optically anisotropic layer.

──────────────────────────────────――
Coating composition for optically anisotropic layer (%)
──────────────────────────────────――
Bar-shaped liquid crystal 28.37
(Paliocolor LC242, manufactured by BASF Japan)
Chiral agent 3.30
(Paliocolor LC756, manufactured by BASF Japan)
Photopolymerization initiator (LC-2-1) 1.32
Additive (LC-1-2) 0.01
Methyl ethyl ketone 67.00
─────────────────────────────────────

ＬＣ−２−１：
ＥＰ１３８８５３８Ａ１に記載された方法で合成した。

LC-2-1:
It was synthesized by the method described in EP1388538A1.

(Preparation of coating liquid LC-3 for optical anisotropic layer)
After the following composition was prepared, it was filtered through a polypropylene filter having a pore size of 0.2 μm and used as a coating liquid LC-3 for an optically anisotropic layer.
──────────────────────────────────――
Coating composition for optically anisotropic layer (%)
──────────────────────────────────――
Rod-shaped liquid crystal (LC-3-1) 6.67
Rod-shaped liquid crystal (LC-3-2) 2.60
Chiral agent (LC-3-3) 21.07
Chiral agent (LC-3-4) 1.67
Chain transfer agent (LC-3-5) 0.67
Photopolymerization initiator (LC-3-6) 0.67
Methyl ethyl ketone 66.65
──────────────────────────────────――

LC-3-1:
Angew. Makromol. Chem. It was synthesized according to the method described in Journal, Vol. 183, p. 45 (1990).
LC-3-2:
It was synthesized by condensing 4- (6-acryloyloxyhexyloxy) benzoic acid synthesized by the method described in EP1174411B1 and 4-propylcyclohexylphenol (manufactured by Kanto Chemical).
LC-3-3:
4- (6-acryloyloxyhexyloxy) benzoic acid synthesized by the method described in EP 1174411B1 and 4-hydroxy-4 ′-(2-methylbutyl) biphenyl synthesized by the method described in WO / 2001040154A1 are condensed. And synthesized.
LC-3-4:
It was synthesized by the method described in EP1389199A1.
LC-3-5:
Hydroxypropyl acrylate (manufactured by Aldrich) was mesylated, reacted with 4-propylcyclohexylphenol (manufactured by Kanto Chemical), and then hydrogen sulfide was added to synthesize.
LC-3-6:
4-Propylcyclohexylphenol (manufactured by Kanto Chemical Co., Ltd.) was triflated to give a biphenyl compound by Suzuki coupling reaction with phenylboronic acid. Furthermore, after acylating the 4′-position of biphenyl with isobutyric chloride and aluminum chloride, the carbon at the α-position of the carbonyl was brominated with bromine and then converted into a hydroxyl group with an alkali.

(Polarized UV irradiation device POLUV-1)
A microwave emission type ultraviolet irradiation device (Light Hammer 10, 240 W / cm, manufactured by Fusion UV Systems) equipped with D-Bulb having a strong emission spectrum at 350 to 400 nm as a UV light source was separated from the irradiation surface by 30 mm. At the position, a wire grid polarizing filter (ProFlux PPL02 (high transmittance type), manufactured by Moxtek) was installed to produce a polarized UV irradiation apparatus. The maximum illuminance of this device was 400 mW / cm ² .

(One-side saponification treatment of cellulose ester film)
The cellulose ester film was passed through a dielectric heating roll having a temperature of 60 ° C. and the film surface temperature was raised to 40 ° C., and then an alkali solution having the composition shown below was applied at 14 ml / m ² using a bar coater. Then, after retaining for 10 seconds under a steam far infrared heater (manufactured by Noritake Co., Ltd.) heated to 110 ° C., 3 ml / m ^{2 of} pure water was applied using the same bar coater. The film temperature at this time was 40 degreeC. Next, washing with a fountain coater and draining with an air knife were repeated three times, and then the sample was retained in a drying zone at 70 ° C. for 2 seconds and dried.
─────────────────────────────
Alkaline solution composition (%)
─────────────────────────────
Potassium hydroxide 4.7
Water 14.7
Isopropanol 64.8
Propylene glycol 14.8
Surfactant (SF-1) 1.0
─────────────────────────────

[Example 1]
After saponifying one side of the transparent support S-1, the alignment layer coating liquid AL-1 was applied thereon with a # 14 wire bar coater, heated at 60 ° C. for 60 seconds, and further at 90 ° C. The film was dried with warm air for 150 seconds to form an alignment layer having a thickness of 1.0 μm. Subsequently, the formed alignment layer is continuously rubbed in the slow axis direction of the transparent support, and then a polymerization reaction with a solid content ratio of 0.5% is applied to the coating liquid LC-1 for optical anisotropic layer. A mixed liquid crystal composition coating solution prepared by adding a controllable UV absorber absorbent (III-1) is applied to the rubbing surface with a # 3 wire bar coater, and heated to dry at 100 ° C. for 1 minute to be uniform. An optically anisotropic layer having a liquid crystal phase was formed. Further, immediately after aging, the transmission axis of the polarizing plate is set to the fast axis direction of the transparent support using POLUV-1 in a nitrogen atmosphere with an oxygen concentration of 0.3% or less with respect to the optically anisotropic layer. The optical compensation sheet of Example 1 was produced by irradiation with polarized UV (illuminance 200 mW / cm ² , irradiation amount 200 mJ / cm ² ). The optically anisotropic layer showed no liquid crystal phase even when heated after fixing. The thickness of the optically anisotropic layer was 1.7 μm.

[Example 2]
In the same manner as in Example 1, except that the amount of the UV absorber absorbent (III-1) added was changed from 0.5% to 1.0% solids ratio, the same as in Example 1. An optical compensation sheet was produced.

[Example 3]
The optical system of Example 3 was the same as Example 1 except that the addition amount of the UV absorber absorbent (III-1) was changed from 0.5% to 1.5% of the solid content ratio. A compensation sheet was prepared.

[Example 4]
Polymerization reaction with 0.5% solid content ratio in place of coating liquid LC-1 for optically anisotropic layer, coating liquid LC-2 for optically anisotropic layer, and UV absorber absorbent (III-1) The optical compensation sheet of Example 4 was produced in the same manner as in Example 1 except that the ultraviolet absorber absorbent (I-1) that can control the pH was added.

[Example 5]
The coating liquid LC-1 for the optically anisotropic layer is replaced with the coating liquid LC-2 for the optically anisotropic layer, and the ultraviolet absorbent (I-1) is replaced with the ultraviolet absorbent (III-1). An optical compensation sheet of Example 5 was produced in the same manner as Example 1 except that 1.0% of the solid content ratio was added.

[Example 6]
The coating liquid LC-1 for the optically anisotropic layer is replaced with the coating liquid LC-2 for the optically anisotropic layer, and the ultraviolet absorbent (I-1) is replaced with the ultraviolet absorbent (III-1). An optical compensation sheet of Example 6 was produced in the same manner as Example 1 except that 1.5% of the solid content ratio was added.

[Example 7]
UV absorber absorbent (III-1) capable of controlling the polymerization reaction with a solid content ratio of 0.5% by replacing coating liquid LC-1 for optically anisotropic layer with coating liquid LC-2 for optically anisotropic layer An optical compensation sheet of Example 7 was produced in the same manner as in Example 1 except that the UV absorber absorbent (I-2) capable of controlling the polymerization reaction with a solid content ratio of 1.0% was changed.

[Example 8]
UV absorber absorbent (III-1) capable of controlling the polymerization reaction with a solid content ratio of 0.5% by replacing coating liquid LC-1 for optically anisotropic layer with coating liquid LC-2 for optically anisotropic layer An optical compensation sheet of Example 8 was produced in the same manner as Example 1 except that the UV absorber absorbent (I-3) capable of controlling the polymerization reaction with a solid content ratio of 1.0% was changed.

[Example 9]
UV absorber absorbent (III-1) capable of controlling the polymerization reaction with a solid content ratio of 0.5% by replacing coating liquid LC-1 for optically anisotropic layer with coating liquid LC-3 for optically anisotropic layer An optical compensation sheet of Example 9 was produced in the same manner as in Example 1 except that the UV absorber absorbent (II-1) capable of controlling the polymerization reaction with a solid content ratio of 1.5% was changed.

[Example 10]
UV absorber absorbent (III-1) capable of controlling the polymerization reaction with a solid content ratio of 0.5% by replacing coating liquid LC-1 for optically anisotropic layer with coating liquid LC-3 for optically anisotropic layer An optical compensation sheet of Example 10 was produced in the same manner as in Example 1 except that the UV absorber absorbent (IV-1) capable of controlling the polymerization reaction with a solid content ratio of 1.5% was changed.

[Example 11]
UV absorber absorbent (III-1) capable of controlling the polymerization reaction with a solid content ratio of 0.5% by replacing coating liquid LC-1 for optically anisotropic layer with coating liquid LC-3 for optically anisotropic layer An optical compensation sheet of Example 10 was produced in the same manner as in Example 1 except that the UV absorber absorbent (IV-2) capable of controlling the polymerization reaction with a solid content ratio of 1.5% was changed.

[Example 12]
UV absorber absorbent (III-1) capable of controlling the polymerization reaction with a solid content ratio of 0.5% by replacing coating liquid LC-1 for optically anisotropic layer with coating liquid LC-3 for optically anisotropic layer An optical compensation sheet of Example 11 was produced in the same manner as in Example 1 except that the UV absorber absorbent (IV-3) capable of controlling the polymerization reaction with a solid content ratio of 1.5% was changed.

[Comparative Example 1]
After saponifying one side of the transparent support S-1, the alignment layer coating liquid AL-1 was applied thereon with a # 14 wire bar coater, heated at 60 ° C. for 60 seconds, and further at 90 ° C. The film was dried with warm air for 150 seconds to form an alignment layer having a thickness of 1.0 μm. Subsequently, the formed alignment layer was continuously rubbed in the slow axis direction of the transparent support, and then the optically anisotropic layer coating liquid LC-1 was applied to the rubbed surface with a # 3 wire bar coater. This was applied and aged by drying at 100 ° C. for 1 minute to form an optically anisotropic layer having a uniform liquid crystal phase. Further, immediately after aging, the transmission axis of the polarizing plate is set to the fast axis direction of the transparent support using POLUV-1 in a nitrogen atmosphere with an oxygen concentration of 0.3% or less with respect to the optically anisotropic layer. Irradiated with polarized UV (illuminance 200 mW / cm ² , irradiation amount 200 mJ / cm ² ), an optical compensation sheet of Comparative Example 1 was produced. The optically anisotropic layer showed no liquid crystal phase even when heated after fixing. The thickness of the optically anisotropic layer was 1.3 μm.

[Comparative Example 2]
An optical compensation sheet of Comparative Example 2 was produced in the same manner as Comparative Example 1 except that the optical anisotropic layer coating liquid LC-1 was replaced with the optical anisotropic layer coating liquid LC-2.

[Comparative Example 3]
An optical compensation sheet of Comparative Example 3 was produced in the same manner as Comparative Example 1 except that the optical anisotropic layer coating liquid LC-1 was replaced with the optical anisotropic layer coating liquid LC-3.

(Phase difference measurement)
With KOBRA 31PRN (manufactured by Oji Scientific Instruments Co., Ltd.), retardation Re (40) and Re (−40) when the sample is tilted ± 40 degrees with the front retardation Re at 589 nm and the slow axis as the rotation axis. It was measured. The results of Examples 1 to 11 and Comparative Examples 1 and 2 are shown in Table 1.

The biaxiality of the produced optical compensation sheet can be easily evaluated by the value obtained by dividing Re by Re (40) (Re / Re (40)). The larger the Re / Re (40), the higher the biaxiality. Means that. About the result shown in the said table | surface, when Example 1 and Comparative Example 1, Example 4, 7, and 8 and Comparative Example 2, and Examples 9-12 and Comparative Example 3 are compared, the ultraviolet absorber will be added. In all the examples, the value of Re / Re (40) was increased as compared with the comparative example. Based on this result, it was confirmed that the biaxiality of the optical compensation sheet can be improved by adding an ultraviolet absorber.
Next, as is clear from Examples 1 to 3 and Examples 4 to 6, the value of Re / Re (40) increases as the amount of the UV absorber added increases, and the biaxiality of the optical compensation sheet increases. Improved. Based on this result, it was confirmed that the biaxiality of the optical compensation sheet can be controlled by the addition amount of the ultraviolet absorber.

(Measurement of dichroic ratio of UV absorber that can control polymerization reaction)
Each of the ultraviolet absorbers (I-1), (I-2) and (I-3) capable of controlling the polymerization reaction in a rod-like liquid crystal (Paliocolor LC242, BASF Japan) and a general photopolymerization initiator of 1.0 % Was added to prepare a 33% by mass MEK solution. This solution was applied onto a rubbing-treated glass substrate by a spin cast method, and dried by heating at 100 ° C. for 1 minute to form an optical anisotropic layer having a uniform liquid crystal phase. Polarization absorption (Ap) parallel to the rubbing direction and orthogonal polarization absorption (As) were measured by polarization absorption spectroscopy, and the ratio (Ap / As) was defined as a dichroic ratio. The results are shown in Table 2.

[Example 12]
(Preparation of polarizing plate with optical compensation sheet)
The optical compensation sheet of Example 6 of the present invention and the commercially available Fujitac TD80UF (Fuji Photo Film Co., Ltd., Re = 3 nm, Rth = 50 nm) were added to a 1.5 mol / L sodium hydroxide aqueous solution at 55 ° C. Immerse for a minute. Subsequently, it was washed in a water bath at room temperature and neutralized at 30 ° C. with 0.05 mol / L sulfuric acid. This was washed again in a room temperature water bath and further dried with hot air at 100 ° C. After this, washing with water and neutralization treatment are performed, and the two saponified films are attached to both surfaces of the polarizing film as a protective film of the polarizing plate by a roll-to-roll using a polyvinyl alcohol-based adhesive. A polarizing plate was produced. All of the examples of the present invention were excellent in productivity, and the optically anisotropic layer exhibited a good surface shape.

[Comparative Example 4]
In Example 12, a polarizing plate with an optical compensation sheet of Comparative Example 4 was produced in the same manner as Example 12 except that the polarizing plate with an optical compensation sheet of Comparative Example 2 was used as the lower polarizing plate.

[Example 13]
(Production of VA-LCD liquid crystal display device)
Strip the upper and lower polarizing plates of a commercially available VA-LCD (SyncMaster 173P, manufactured by Samsung Electronics Co., Ltd.), the upper side is a normal polarizing plate, the lower side is a polarizing plate with an optical compensation sheet of Example 12 of the present invention, The liquid crystal display device of the present invention was prepared by pasting with an adhesive such that the optically anisotropic layer was on the liquid crystal cell substrate glass surface. FIG. 4A shows a schematic cross-sectional view of the manufactured liquid crystal display device together with the angular relationship of the optical axes of the respective layers. In FIG. 4A, 41 is a polarizing layer, 42 is a transparent support, 43 is an alignment layer, 44 is an optically anisotropic layer (41 to 44 constitute the optical compensation sheet of the present invention), and 45 is polarized light. A plate protective film, 46 is a glass substrate for a liquid crystal cell, 47 is a liquid crystal cell, and 48 is an adhesive layer. Further, the arrow in the polarizing layer 41 indicates the direction of the absorption axis, the arrow in the optically anisotropic layer 44 or its support 44 and the protective film 45 indicates the direction of the slow axis, and the circle indicates the direction of the arrow relative to the paper surface. Indicates the line direction.

[Comparative Example 5]
A liquid crystal display device of Comparative Example 5 was produced in the same manner as in Example 13 except that the polarizing plate with an optical compensation sheet of Comparative Example 4 was used as the lower polarizing plate in Example 13.

(Evaluation of VA-LCD liquid crystal display device)
The viewing angle characteristics of the manufactured liquid crystal display device were measured with a viewing angle measuring device (EZ Contrast 160D, manufactured by ELDIM). Furthermore, when the 45-degree oblique direction was also evaluated visually, excellent contrast characteristics were obtained.

It is a schematic sectional drawing which shows an example of the functional film of this invention. It is a schematic sectional drawing which shows an example of the polarizing plate of this invention. It is the schematic which shows an example of the liquid crystal display device of this invention. It is the schematic sectional drawing which showed the layer structure of the liquid crystal display device produced in Example 13 and Comparative Example 5 with the direction of the optical axis in a layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Transparent support 12 Optically anisotropic layer 13 which consists of liquid crystalline compound Orientation layer 21 Polarizing layers 22, 23 Protective film 24 Functional layer 31, such as (lambda) / 4 board, anti-reflective film, Cold cathode tube 32 Reflective sheet 33 Light guide plate 34 Light control film 35 such as brightness enhancement film, diffusion film, etc. Liquid crystal cell 36 Lower polarizing plate 37 Upper polarizing plate 41 Polarizing layer 42 Transparent support 43 Orientation layer 44 Optical anisotropic layer 45 Polarizing plate protective film 46 Glass for liquid crystal cell Substrate 47 Liquid crystal cell 48 Adhesive 51 Uniaxially stretched optical compensation sheet

Claims (16)

Optical formed from a composition comprising a transparent support, an alignment layer on the support, and at least one type of polymerizable liquid crystal compound and at least one type of ultraviolet absorber for suppressing the polymerization reaction on the surface of the alignment layer Having an anisotropic layer, the front retardation (Re) of the optically anisotropic layer is not 0,
Retardation value measured by injecting light of wavelength λ nm from a direction inclined + 40 ° with respect to the normal direction with the in-plane slow axis as the tilt axis (rotation axis), and the in-plane slow axis as the tilt axis An optical compensation sheet having substantially the same retardation value measured by making light having a wavelength λ nm incident from a direction inclined by −40 ° with respect to the normal direction as a rotation axis. The optical compensation sheet according to claim 1, wherein the polymerizable liquid crystal compound is a polymerizable rod-like liquid crystal compound, and the optically anisotropic layer is a layer formed by a polymerization reaction of a polymerizable group of the liquid crystal compound. The optical compensation according to claim 1 or 2, wherein the composition further contains at least one chiral agent, and the optically anisotropic layer is a layer formed by polymerizing a polymerizable group of the polymerizable liquid crystal compound. Sheet. The optical compensation sheet according to any one of claims 1 to 3, wherein the optically anisotropic layer is a layer formed by irradiating polarized light after cholesteric alignment of the rod-like liquid crystal compound molecules. 5. The layer according to claim 1, wherein the alignment layer is a layer formed from a composition containing at least one polymer having a polymerizable group in a side chain, or at least one monomer or oligomer having a polymerizable group. 2. The optical compensation sheet according to item 1. 6. The optical compensation sheet according to claim 5, wherein the polymer having a polymerizable group in the side chain is a modified polyvinyl alcohol having a polymerizable group. The optical compensation sheet according to claim 5 or 6, wherein the polymerizable group of the polymer is a polymerizable group containing an ethylene group or a cyclic ether group. The ultraviolet absorber is oriented in the same direction as the rod-like liquid crystal compound in a uniaxially oriented rod-like liquid crystal compound, and its absorption exhibits dichroism in the ultraviolet region. The optical compensation sheet according to 1. The optical compensation sheet according to any one of claims 1 to 8, wherein the ultraviolet absorber is an ultraviolet absorber represented by the following general formulas (I) to (III):

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and each may have a substituent;

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and each may have a substituent;

In the formula, Ar ¹ and Ar ² each independently represent an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, each of which may have a substituent; Y represents an oxygen atom, Represents a sulfur atom or a nitrogen atom; Z represents a carbon atom or a nitrogen atom. The optical compensation sheet according to any one of claims 1 to 8, wherein the ultraviolet absorber is an ultraviolet absorber represented by the following general formula (IV).

In the formula, Ar ¹ represents an aromatic ring having 5 to 14 carbon atoms or a heterocyclic ring having 5 to 14 carbon atoms, and may have a substituent; each of W ¹ and W ² independently represents a hydrogen atom or An electron withdrawing group is represented, and V ¹ represents an electron withdrawing group. The optical compensation sheet according to claim 1, wherein the ultraviolet absorber is a compound having a polymerizable group. The optical compensation sheet according to claim 1, wherein the transparent support contains a cellulose-based or cycloolefin-based polymer. A step of forming an alignment layer by applying a composition containing at least one polymer and / or at least one monomer on a transparent support, a liquid crystal compound having at least one polymerizable group, and at least one polymerization reaction Applying a coating liquid of a liquid crystal composition containing an ultraviolet absorber that suppresses at least one chiral agent on the alignment layer, cholesteric alignment of molecules of the liquid crystalline compound with an average tilt angle of less than 5 °, 2. The method for producing an optical compensation sheet according to claim 1, wherein the steps of simultaneously irradiating polarized light and performing optical biaxial expression and polymerization are performed in this order. A polarizing plate comprising the optical compensation sheet according to claim 1 and a polarizer. A liquid crystal display device comprising the optical compensation sheet according to claim 1 or the polarizing plate according to claim 14. The liquid crystal display device according to claim 15, wherein the display mode is a VA mode.

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