JP4832796B2 - Optical compensation sheet, polarizing plate, and liquid crystal display device - Google Patents

Description

  The present invention relates to an optical compensation sheet, a polarizing plate, and a liquid crystal display device. More specifically, the present invention relates to an optical compensation sheet and a polarizing plate that contribute to improving the viewing angle characteristics of a vertical alignment (VA) mode liquid crystal display device, and viewing angle characteristics. The present invention relates to an excellent vertical alignment (VA) mode liquid crystal display device.

  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 (optical compensation sheet). . 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.

  Moreover, although a stretched film is normally used for positive a-plate, when using the longitudinally stretched film in a continuous conveyance process, the slow axis of a-plate turns into the film conveyance (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 has been proposed instead of the combination of c-plate and a-plate (Non-patent Document 2). By using a biaxial retardation plate, there is an advantage that not only the contrast viewing angle but also the color can be improved, but the biaxial stretching usually used for producing a biaxial retardation plate is a lateral Similar to stretching, uniform axis control over the entire region of the film is difficult, and the yield does not increase, resulting in an increase in cost. However, in biaxial stretching, if the ratio between the longitudinal stretching ratio and the lateral stretching ratio is changed, it is necessary to adjust the axis control for each magnification, and the yield is significantly reduced.
Therefore, a biaxial retardation plate is produced without using stretching by a method of irradiating polarized violet light to a special cholesteric liquid crystal (Patent Document 3) or a method of irradiating a special disk-shaped liquid crystal to polarized ultraviolet light (Patent Document 4). A way to do it was proposed. By this method, various problems caused by stretching can be solved.

On the other hand, in the VA mode viewing angle compensation, it is necessary to control the biaxiality for each cell gap of the liquid crystal cell. That is, in order to perform optical compensation in accordance with the liquid crystal cell, light having a wavelength λ nm is obtained from a direction inclined + 40 ° with respect to the normal direction of the optical compensation sheet with the front retardation Re and the in-plane slow axis as the inclination. It is required to adjust Re / Re (40), which is a ratio to the retardation value measured by incidence, for each cell gap of the liquid crystal cell. However, a method for controlling the Re / Re (40) value according to the liquid crystal cell has not been found so far.
Japanese Patent Laid-Open No. 2-176625 JP 2000-304930 A EP1389199 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 in which a liquid crystal cell is accurately optically compensated and excellent in productivity, a polarizing plate using the same, and a liquid crystal display device. In particular, it is to provide a device used for a VA mode liquid crystal display device.

Means for solving the above problems are as follows.
[1] An optical compensation sheet having an alignment layer and an optically anisotropic layer in this order on a transparent support,
The optically anisotropic layer includes a liquid crystalline compound having at least one reactive group, a polymerization initiator having dichroism in at least one ultraviolet region, a polymerization initiator having no dichroism, and / or It is formed by curing a liquid crystal layer formed by applying and drying a solution for forming an optically anisotropic layer containing a photosensitizer having no dichroism on the alignment layer,
The front retardation (Re) of the optically anisotropic layer is not 0, and the wavelength λ nm from the direction inclined + 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 light having a wavelength of λ nm is incident from the direction inclined by −40 ° with respect to the normal direction of the optical compensation sheet, with the retardation value measured by the incident light and the in-plane slow axis as the tilt axis (rotation axis) An optical compensation sheet characterized in that the measured retardation values are substantially equal.
[2] The optical compensation sheet according to [1], wherein the alignment layer is formed by applying and drying an alignment layer forming solution on the transparent support.
[3] The optical compensation sheet according to [2], wherein the alignment layer forming solution contains a polymer having a reactive group in a side chain, or a monomer or oligomer having a reactive group.
[4] The optical compensation sheet according to [3], wherein the alignment layer forming solution contains a modified polyvinyl alcohol having a reactive group in a side chain.
[5] The optical compensation sheet according to any one of [1] to [4], wherein the liquid crystal compound has at least one ethylenically unsaturated group.
[6] The optical compensation sheet according to any one of [3] to [5], wherein the reactive group of the liquid crystal compound can react with the reactive group of the alignment layer.
[7] The optical compensation sheet according to any one of [1] to [6], wherein the transparent support is a cellulose-based or cycloolefin-based polymer.
[8] The optical compensation sheet according to any one of [1] to [7], wherein the optically anisotropic layer is formed by irradiating the liquid crystal layer with polarized ultraviolet rays.
[9] The optical compensation sheet according to [8], wherein the surface temperature of the liquid crystal layer is maintained in the range of 70 to 160 ° C. in the irradiation with polarized ultraviolet rays.
[10] The optical compensation sheet according to [8] or [9], wherein the optically anisotropic layer exhibits a cholesteric phase before irradiation with polarized ultraviolet rays.
[11] The optical compensation sheet according to any one of [1] to [10], wherein the liquid crystalline compound is a rod-like liquid crystalline compound.
[12] A polarizing plate comprising the optical compensation sheet according to any one of [1] to [11] and a polarizing film.
[13] A liquid crystal display device having the optical compensation sheet according to any one of [1] to [11] or the polarizing plate according to [12].
[14] The liquid crystal display device according to [13], wherein the display mode is a VA mode.

  By using the optical compensation sheet of the present invention, it becomes possible to optically compensate the liquid crystal cell with the same configuration as the conventional liquid crystal display device, and further, the liquid crystal display device of the present invention having the optical compensation sheet. In addition to display quality, the viewing angle is remarkably improved. Further, according to the present invention, an optical compensation sheet that can be adjusted biaxially with respect to cell gaps of different liquid crystal cells can be stably produced with high productivity.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  In the present invention, Re, which is front retardation, and Rth, which is retardation in the thickness direction, is calculated based on the following. Re and Rth respectively represent in-plane retardation and retardation in the thickness direction at the wavelength λ. Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) by making light of wavelength λ nm incident in the normal direction of the film. Rth is Re, and the in-plane slow axis (determined by KOBRA 21ADH) is used as the tilt axis (rotary axis) and the angle is changed with respect to the normal direction of the film, and light having a wavelength of λ nm is incident from the tilted direction. KOBRA 21ADH is calculated based on a plurality of retardation values measured in this manner. At this time, it is necessary to input an assumed value of average refractive index and a film thickness. KOBRA 21ADH calculates nx, ny, and nz in addition to Rth. The average refractive index of 1.48 is used for cellulose acetate, but the 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, a polymer handbook (John Wiley & Sons, Inc.) or a catalog value of a polymer film can be used. Further, in the case of a material whose average refractive index is unknown, it can be measured using an Abbe refractometer. In this specification, λ refers to 545 ± 5 nm or 590 ± 5 nm unless otherwise specified.

  In the present invention, “substantially” for the angle means that the error from the exact angle is within a range of less than ± 5 °. Furthermore, the error from the exact angle is preferably less than 4 °, more preferably less than 3 °. With regard to retardation, “substantially” means that the retardation is within ± 5%. Furthermore, “Re is not 0” means that Re is 1 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 invention, “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 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 curing a composition containing at least one liquid crystalline compound. On the other hand, the alignment layer 13 positioned below the optically anisotropic layer 12 is a polymer layer formed by applying and drying a solution containing a polymer. The optically anisotropic layer 12 can be a layer formed by fixing a cholesteric phase. In the present invention, a liquid crystal cell, preferably a VA mode liquid crystal cell, can be optically compensated accurately using an optically anisotropic layer formed by fixing the cholesteric phase.

  The optical properties of the optically anisotropic layer 12 were not zero in front retardation (Re), and were inclined + 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 value measured by making light of wavelength λnm incident from the direction, and the wavelength λnm from the 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) If the retardation value measured by making the incident light is adjusted to be substantially equal, a biaxial medium is obtained, and a liquid crystal cell, particularly a VA mode liquid crystal cell, can be compensated more accurately.

[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 arranged on the polarizing plate having the configuration shown in FIG. FIG. 2C is a configuration example in which another functional layer 24 is arranged on the protective film 23 arranged 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 can arrange | position 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 includes a support that supports the optically anisotropic layer, and the support also serves as a protective film for the polarizing plate, or the optically anisotropic layer serves as a protective film for the polarizing plate. By serving also, the structural member of a 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 formed by curing a composition (solution for forming an optically anisotropic layer) containing at least one liquid crystalline compound. 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.

  As described above, in the present invention, the optically anisotropic layer contributes to optically compensate 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 a liquid crystalline compound having at least one reactive group. 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. Two or more kinds of rod-like liquid crystalline compounds or a mixture of rod-like liquid crystalline compounds and discotic liquid crystalline compounds may be used. It is more preferable to form an optically anisotropic layer by using a rod-like liquid crystalline compound having a reactive group, because at least one of the reactive groups in one liquid crystal molecule can be formed. Is more preferably 2 or more. The liquid crystalline compound may be a mixture of two or more, and in that case, at least one preferably has two or more reactive 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. As the rod-like liquid crystalline compound having a low molecular polymerizable group which is particularly preferably used, a rod-like liquid crystalline compound represented by the following general formula (I) can be exemplified.

Formula (I): 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 At least one of L ⁴ is preferably —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 (I) 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 the formula (I), Q ¹ -L ¹ and Q ² -L ² -are CH ₂ ═CH—CO—O—, CH ₂ ═C (CH ₃ ) —CO—O—, and CH ₂ ═C ( Cl) -CO-O-CO- O- are _{preferable, CH 2 = CH-CO-} O- is most preferable.

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 (II) is preferable.
Formula (II): - (- 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 groups represented by L ^{1 to} L ⁴ in the formula (I), —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 (II) are shown below. These may be substituted with the above substituents.

  Examples of the compound represented by the general formula (I) are shown below, but the present invention is not limited thereto. The compound represented by the general formula (I) 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, Paliocolor LC242, Paliocolor LC756, BASF Japan etc. can be used.

  The optically anisotropic layer of the present invention contains at least one polymerization initiator having dichroism in the ultraviolet region (hereinafter also referred to as “dichroic polymerization initiator”). The dichroic polymerization initiator has a property of absorbing a polarized light having a specific polarization plane when it has an absorption at 180 to 420 nm and is mixed with a rod-like liquid crystalline compound to form a liquid crystal phase. The property is that in a parallel cell in which an arbitrary rod-like liquid crystal compound is added and enclosed in a cell composed of two glass substrates having an alignment layer arranged in parallel in the rubbing direction, polarized light parallel to the rubbing direction and It can be confirmed that the ratio of the absorption peak due to the polymerization initiator 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. The polymerization initiator having dichroism in the ultraviolet region is not particularly limited as long as the above conditions are satisfied, but has a mesogenic group as described above, that is, the molecular length of a rigid structure is relatively long. A long structure is preferred. Examples of such polymerization initiators include the polymerization initiators described in EP-A-1388538.

  The optically anisotropic layer of the present invention has a polymerization initiator that does not have dichroism in the ultraviolet region (hereinafter also referred to as “non-dichroic polymerization initiator”) and / or light that does not have dichroism. At least one sensitizer (hereinafter also referred to as “non-dichroic photosensitizer”) is included. Not having dichroism in the ultraviolet region means absorption at 180 to 420 nm and absorption of all polarized light regardless of the plane of polarization. The property is that in a parallel cell in which an arbitrary rod-like liquid crystal compound is added and enclosed in a cell composed of two glass substrates having an alignment layer arranged in parallel in the rubbing direction, polarized light parallel to the rubbing direction and It can be confirmed that the ratio of the absorption peak caused by the polymerization initiator or photosensitizer to the orthogonally polarized light is 75 to 125%. As an absorption peak wavelength, 300-400 nm is preferable and 350-380 nm is especially preferable. The polymerization initiator or photosensitizer that does not have dichroism in the ultraviolet region is not particularly limited as long as the above conditions are satisfied, but does not have a mesogenic group as described above, that is, it is rigid. It is preferable that the structure has a short molecular length.

  The dichroic polymerization initiator and the non-dichroic polymerization initiator preferably react with the reactive group of the liquid crystal compound and the compound constituting the alignment layer, and particularly polymerize the ethylenically unsaturated group. preferable. A photopolymerization initiator that absorbs ultraviolet rays to initiate polymerization is preferred, and a radical photopolymerization initiator is particularly preferred. 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 non-dichroic photosensitizer preferably has a sensitizing action on the photopolymerization initiator that reacts the liquid crystalline compound and the reactive group of the compound constituting the alignment layer. Specific examples of non-dichroic polymerization initiators and non-dichroic photosensitizers include: UV / EB Curing Handbook-Raw Material Edition, Kato Kiyomi Edition, pages 67-73, Polymer Publishing Association (1985) ).

  A chiral agent can also be added to the optical anisotropic layer forming solution. The chiral agent preferably 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, chiral agents described in European Patent No. 1388538, pages 16 and 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). Re (40), and retardation value Re 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) (−40) has the optical characteristic of being substantially equal. 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 is gradually changed in the thickness direction. Can be used to select a method of distorting by polarized light irradiation (International Publication WO03 / 054111A1).

  The preferred Re, Re (40) and Re (−40) of the optically anisotropic layer vary depending on the layer structure (arrangement, number) of the retardation film and the cell gap of the liquid crystal cell, but black at all azimuth angles. It is preferable to design so that the black transmittance at the time of display is kept low even at a high incident angle. T (45 °, 0 °, 550 nm) / T (45 °, 60 nm) where T (φ, θ, λ) is the transmittance of light of wavelength λ at the azimuth angle φ and polar angle θ during black display. °, 550 nm) is preferably 0.5 to 4, more preferably 0.6 to 3, and most preferably 0.8 to 2. If the cell gap of the liquid crystal cell changes, the preferred Re of the optically anisotropic layer changes, so it is preferable that Re and Re (40) of the optically anisotropic layer can be freely changed.

  In the present invention, the physical properties of the liquid crystal cell are adjusted by adjusting the addition amount of the dichroic polymerization initiator, the non-dichroic polymerization initiator, the non-dichroic photosensitizer, and the thickness of the optically anisotropic layer. It is possible to obtain an optical compensation sheet having optical properties corresponding to the physical properties. Specifically, the retardation and biaxiality of the optically anisotropic layer, particularly Re / Re (40), can be controlled by controlling the amount of each component added and the thickness of the optically anisotropic layer. It can be controlled to a value according to. The amount of the dichroic polymerization initiator used is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, based on the solid content of the coating solution. The amount of the non-dichroic polymerization initiator used is preferably 0 to 5% by mass, more preferably 0 to 3% by mass, based on the solid content of the coating solution, and the non-dichroic photosensitizer. Is preferably 0 to 5% by mass, more preferably 0 to 3% by mass, based on the solid content of the coating solution. The thickness of the optically anisotropic layer can be, for example, 0.5 to 5 μm, preferably 0.8 to 4 μm, and more preferably 1 to 3 μm.

  When two or more optically anisotropic layers containing a liquid crystalline compound are laminated, the combination of the liquid crystalline compounds is not particularly limited, and all the rod-like liquid crystals may be a laminate of layers made of discotic liquid crystalline compounds. It may be a laminate of layers made of a volatile compound, or a laminate of layers made of a discotic liquid crystalline compound and a layer made of a rod-like liquid crystalline compound. 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. In particular, the optically anisotropic layer preferably exhibits a cholesteric phase before irradiation with polarized ultraviolet rays.

  The optically anisotropic layer is an alignment layer obtained by rubbing a coating liquid (solution for forming an optically anisotropic layer) containing a liquid crystalline compound and the aforementioned polymerization initiator, photosensitizer and other additives. On top of this, it can be formed preferably by direct application and drying. 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). Of these, 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).

[Optical alignment by polarized irradiation]
The optically anisotropic layer of the optical compensation sheet of the present invention can generate in-plane retardation by photo-alignment by irradiation with polarized light. This polarized light irradiation may be performed simultaneously with the photopolymerization process in the alignment fixation of the liquid crystalline compound, or may be further fixed by non-polarized light after first polarized light irradiation, or may be performed first by non-polarized light irradiation. Photo-alignment may be carried out by irradiation with polarized light after being fixed to the substrate. 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. The polarized light irradiation is preferably ultraviolet polarized light irradiation, particularly preferably polarized light irradiation having a peak at 365 ± 10 nm, and more preferably polarized light irradiation having a peak at 365 ± 5 nm. 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. In polarized UV irradiation, it is preferable to keep the surface temperature of the liquid crystal layer in the range of 70 to 160 ° C. 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 of the compounds represented by the following general formulas (1) to (3) in the optical anisotropic layer forming solution, the molecules of the liquid crystalline compound can be substantially horizontally aligned. it can. 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. The horizontal plane of the transparent support is parallel, but it is not required to be strictly parallel, and in the present invention, it means an orientation having an inclination angle of less than 10 degrees with the horizontal plane. . 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 (1) to (3) 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 — or the group. It is more preferably a divalent linking group in which at least two groups are combined. 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 recited 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 preferably the substituents represented by R ¹ , R ² and R ³ in the general formula (I). 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 amount of the compound represented by the general formulas (1) to (3) 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 (1) to (3) may be used alone or in combination of two or more.

[Alignment layer]
The optical compensation sheet of the present invention has an alignment layer between the transparent support and the optically anisotropic layer. In order to align the liquid crystalline compound, a predetermined polymer layer is preferably used as the alignment layer. The alignment layer is generally an organic compound (for example, ω-tricco) by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroup, or 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 treatment can be performed by rubbing the surface of the polymer layer with paper or cloth several times in a certain direction.

  In the present invention, a polymer layer formed by applying and drying the alignment layer forming solution is preferably used as the alignment layer. For forming the alignment layer, it is preferable to use a polymer. 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 alignment layer forming solution preferably contains a polymer having a reactive group in the side chain, or a monomer or oligomer having a reactive group, specifically, a modified polyvinyl alcohol having a reactive group in the side chain. Examples of the reactive group include the reactive groups described above. Moreover, it is preferable that a reactive group can react directly with the reactive group which the liquid crystalline compound used for an optically anisotropic layer has. When the compound of the alignment layer and the optically anisotropic layer undergoes a direct crosslinking reaction, the adhesion of the completed film can be imparted.

  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 the optically anisotropic layer directly without transfer.

  Each layer of the optically 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). Etc.) can be formed by coating. Two or more layers may be applied simultaneously. The methods of simultaneous application are 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]
In the present invention, a polymer film having a light transmittance of 80% or more is preferably used as the transparent support. 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 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.

  As the polymer constituting the transparent support, for example, a cellulose polymer and a cycloolefin polymer can be used. Specifically, cellulose ester (eg, cellulose acetate, cellulose propionate, cellulose butyrate), polyolefin (eg, norbornene polymer), poly (meth) acrylic acid ester (eg, polymethyl methacrylate), polycarbonate, polyester And polysulfone can be used. 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, cellulose ester is preferable, and cellulose lower fatty acid ester 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 mass of the amount of cellulose ester, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass.

  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 mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the addition amount exceeds 1% by mass, 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.

  A retardation control agent can be added to the cellulose ester film in order to control Re and Rth. 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 each pamphlet of International Publication Nos. 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 can be cast on a drum or band and the solvent evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 10 to 40% by mass. The solid content is more preferably 18 to 35% by mass. Two or more dopes can be cast. The surface of the drum or band is preferably finished in a mirror state. As for casting and drying methods in the solvent casting method, 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 obtain a preferable moisture permeability range as a protective film for the polarizing plate by adjusting the thickness. 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 for the optically anisotropic layer is protected for the polarizing plate. A polarizing plate that can also serve as a film and has optical compensation ability can be manufactured at low cost with high productivity.

[Polarizer]
The polarizing plate of the present invention has the above-described optical compensation sheet of the present invention and a polarizing film. The polarizing plate usually 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 size 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 polarizing plate of the present invention preferably has optical properties and durability (short-term and long-term storage stability) equivalent to or better than those of commercially available super high contrast products (for example, HLC2-5618 manufactured by Sanlitz Co., Ltd.). . 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 preferable that the change rate of the polarization degree is 1% or less, further 1% or less, further 0.1% or less based on the absolute value.

[Liquid Crystal Display]
The liquid crystal display device of the present invention has the above-described optical compensation sheet or polarizing plate of the present invention. The display mode of the liquid crystal display device of the present invention is not particularly limited, but the VA mode is preferable. The liquid crystal display device of the present invention is effective not only in the display mode but also in an aspect applied to the STN mode, TN mode, and 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.

  As shown in FIG. 3, transparent electrodes are formed inside the upper and lower substrates of the liquid crystal cell 35, but in a non-driving state in which no driving voltage is applied to the electrodes, the liquid crystal molecules in the liquid crystal layer are roughly with respect to the substrate surface. As a result, the polarization state of light passing through the liquid crystal panel is hardly changed. Since the absorption axis of the upper polarizing plate 37 of the liquid crystal cell 35 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 fast 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, this problem can be solved by providing at least one optically anisotropic layer on a transparent support having predetermined optical properties.

  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 features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. In addition, “%” described below indicates “% by mass” unless otherwise specified.

(Preparation of transparent support S-1)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.
────────────────────────────────────――
Cellulose acetate solution composition (%)
────────────────────────────────────――
Cellulose acetate with an acetylation degree of 60.7-61.1% 20.5
Triphenyl phosphate (plasticizer) 1.6
Biphenyl diphenyl phosphate (plasticizer) 0.8
Methylene chloride (first solvent) 68.9
Methanol (second solvent) 5.9
1-butanol (third solvent) 2.3
────────────────────────────────────――

The following composition was put into another mixing tank and stirred while heating to dissolve each component to prepare a retardation increasing agent solution.
────────────────────────────────────――
Retardation increasing agent solution composition (%)
────────────────────────────────────――
Retardation increasing agent (A-1) 13.7
Methylene chloride 79.3
Methanol 7.0
────────────────────────────────────――
The cellulose acetate solution and the retardation increasing agent solution were mixed at a ratio (mass ratio) of 95: 5 and sufficiently stirred to prepare a dope.

  The obtained dope was cast using a band stretching machine. After the film surface temperature on the band reached 40 ° C., the film was dried with warm air of 70 ° C. for 1 minute, and the film was dried from the band with 140 ° C. drying air for 10 minutes, and the residual solvent amount was 0.3% by mass. A cellulose acetate film (thickness: 80 μm) was prepared. About the produced cellulose acetate film (transparent support body, transparent protective film), Re retardation value and Rth retardation value in wavelength 589nm were measured using KOBRA 21ADH (Oji Scientific Instruments Co., Ltd. product). Re was 8 nm and Rth was 78 nm.

(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 described 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 optically anisotropic layers. Photopolymerization initiator (dichroic polymerization initiator) LC-1-1 was synthesized by the method described in EP1388538A1, page 21.
──────────────────────────────────――
Coating composition for optically anisotropic layer (%)
──────────────────────────────────――
Bar-shaped liquid crystal (Paliocolor LC242, BASF Japan) 28.38
Chiral agent (Paliocolor LC756, BASF Japan)
3.30
Photopolymerization initiator (LC-1-1) 1.32
Methyl ethyl ketone 67.00
──────────────────────────────────――

(Preparation of coating liquid LC-2 for optically anisotropic layer)
After preparing the following composition, it was filtered through a polypropylene filter having a pore size of 0.2 μm and used as a coating liquid LC-2 for an optically anisotropic layer.
───────────────────────────────────――
Coating composition for optically anisotropic layer (%)
───────────────────────────────────――
Bar-shaped liquid crystal (Paliocolor LC242, BASF Japan) 28.35
Chiral agent (Paliocolor LC756, BASF Japan) 3.30
Photopolymerization initiator (LC-1-1) 1.32
Non-dichroic photosensitizer (Kayacure DETX-S, manufactured by Nippon Kayaku Co., Ltd.) 0.03
Methyl ethyl ketone 67.00
───────────────────────────────────――

(Preparation of coating liquid LC-3 for optically anisotropic layer)
After preparing the following composition, it filtered with the polypropylene filter with the hole diameter of 0.2 micrometer, and used as coating liquid LC-3 for optically anisotropic layers.
───────────────────────────────────――
Coating composition for optically anisotropic layer (%)
───────────────────────────────────――
Bar-shaped liquid crystal (Paliocolor LC242, BASF Japan) 28.31
Chiral agent (Paliocolor LC756, BASF Japan) 3.30
Photopolymerization initiator (LC-1-1) 1.32
Non-dichroic photosensitizer (Kayacure DETX-S, manufactured by Nippon Kayaku Co., Ltd.) 0.07
Methyl ethyl ketone 67.00
───────────────────────────────────――

(Preparation of coating liquid LC-4 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-4 for an optically anisotropic layer.
───────────────────────────────────――
Coating composition for optically anisotropic layer (%)
───────────────────────────────────――
Bar-shaped liquid crystal (Paliocolor LC242, BASF Japan) 28.22
Chiral agent (Paliocolor LC756, BASF Japan) 3.30
Photopolymerization initiator (LC-1-1) 1.32
Non-dichroic photosensitizer (Kayacure DETX-S, manufactured by Nippon Kayaku Co., Ltd.) 0.16
Methyl ethyl ketone 67.00
───────────────────────────────────――

(Preparation of coating liquid LC-5 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-5 for an optically anisotropic layer.
───────────────────────────────────――
Coating composition for optically anisotropic layer (%)
───────────────────────────────────――
Bar-shaped liquid crystal (Paliocolor LC242, BASF Japan) 27.39
Chiral agent (Paliocolor LC756, BASF Japan) 3.30
Photopolymerization initiator (LC-1-1) 1.32
Non-dichroic photopolymerization initiator (Irgacure 907, manufactured by Ciba Specialty Chemicals Co., Ltd.) 0.99
Methyl ethyl ketone 67.00
───────────────────────────────────――

(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 cm. 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
─────────────────────────────

[Optical compensation sheets A to E]
After saponifying one side of the transparent support S-1 using the above-described one-side saponification method, the coating liquid AL-1 for alignment layer is applied thereon with a # 14 wire bar coater, and warm air at 60 ° C. For 60 seconds and then with warm air at 90 ° C. for 150 seconds to form an alignment layer having a thickness of 1.0 μm. Subsequently, after rubbing the formed alignment layer with respect to the slow axis direction of the transparent support, the coating liquid LC-1 to 5 for the optically anisotropic layer was applied thereon with a # 3 wire bar coater. Then, the film surface temperature was 95 ° C. for 2 minutes by heat drying to form an optically anisotropic layer having a uniform liquid crystal phase. Further, immediately after aging, the transmission axis of the polarizing filter is in the slow axis direction of the transparent support using the polarized UV irradiation device POLUV-1 in a nitrogen atmosphere with an oxygen concentration of 0.3% or less with respect to the optically anisotropic layer. In this way, polarized UV rays were irradiated (illuminance 200 mW / cm ² , irradiation amount 200 mJ / cm ² ) to fix the optically anisotropic layer, and optical compensation sheets A to E were produced. The optically anisotropic layer showed no liquid crystal phase even when heated after fixing. The thickness of the optically anisotropic layer was 1.4 μm.

[Optical compensation sheet F]
An optical compensation sheet F was produced in the same manner as described above except that the coating liquid LC-1 for optically anisotropic layer was applied with a # 2.1 wire bar coater. The optically anisotropic layer did not show a liquid crystal phase even when heated after fixing. The thickness of the optically anisotropic layer was 1.0 μm.

(Phase difference measurement)
Retardation Re (40) and Re (−40) when a sample is tilted ± 40 degrees with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) and front retardation Re at 589 nm and the slow axis as the rotation axis. It was measured. The phase difference of the optically anisotropic layer was determined by subtracting the phase difference of the support at each angle from the phase difference of the entire optical compensation sheet at each angle.

  Table 1 shows the retardation measurement results of the optically anisotropic layers of the optical compensation sheets A to F.

  As shown in Table 1, a dichroic polymerization initiator and a non-dichroic polymerization initiator or a non-dichroic sensitizer are used in combination, and the addition amount of the non-dichroic polymerization initiator or the non-dichroic sensitizer It was possible to adjust Re, Re (40), Re (−40), and Re / Re (40). From the data of sample F, Re, Re (40), and Re (−40) are adjusted by adjusting the film thickness even when the non-dichroic polymerization initiator or the non-dichroic sensitizer is not used. It was found that Re / Re (40) cannot be changed.

(Production of liquid crystal cells C-1 and C-2)
In the liquid crystal cells C-1 and C-2, the cell gap between the substrates is 3 μm and 3.2 μm, respectively, and a liquid crystal material having negative dielectric anisotropy (“MLC-6608”, manufactured by Merck & Co., Inc.) is used. A liquid crystal layer was formed between the substrates by dropping and sealing between the substrates. The retardation of the liquid crystal layer was 300 nm and 320 nm, respectively. The liquid crystal material was aligned so as to be vertically aligned.

(Preparation of polarizing plate P-1)
Two commercially available Fujitac TD80UF (Fuji Photo Film Co., Ltd., Re = 3 nm, Rth = 50 nm) were immersed in a 1.5 mol / L sodium hydroxide aqueous solution at 55 ° C. for 2 minutes. 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. Thereafter, washing with water and neutralization treatment were performed, and the two saponified films were attached to both surfaces of the polarizing film as a protective film of a polarizing plate by a roll-to-roll using a polyvinyl alcohol-based adhesive.

(Preparation of polarizing plates P-2 and P-3 with optical compensation sheet)
A commercially available optical compensation sheet made of uniaxially stretched arton (Re = 81 nm) is bonded to one side of the polarizing plate P-1 with an adhesive so that the slow axis coincides with the transmission axis of the polarizing plate, and further The optical compensation sheet B or F is bonded with an adhesive with the optically anisotropic layer facing outward so that the slow axis coincides with the transmission axis of the polarizing plate, whereby the polarization having the optical compensation sheet B is obtained. P-3 having a plate P-2 and an optical compensation sheet F was produced.

[Example 1, Comparative Examples 1 and 2]
(Production of VA-LCD liquid crystal display device)
A normal polarizing plate is bonded to the upper side of the prepared liquid crystal cell, a polarizing plate P-2 or P-3 is bonded to the lower side, and an optically anisotropic layer is bonded to the liquid crystal cell substrate glass surface with an adhesive. Thus, a liquid crystal display device was produced. Table 2 shows combinations of the liquid crystal cell and the polarizing plate with the optical compensation sheet. FIG. 4 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. 4, 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 an optical compensation sheet), 45 is a polarizing 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. Moreover, the arrow in the polarizing layer 41 shows the direction of an absorption axis, and the arrow in the optically anisotropic layer 44, its support body 44, and the protective film 45 shows the direction of a slow axis.

(Evaluation of VA-LCD liquid crystal display device)
The viewing angle characteristics in black display of the manufactured liquid crystal display device were measured using a light luminance measuring device (“BM5A” manufactured by Topcon). FIG. 5 shows the incident angle dependence of luminance at an azimuth angle of 45 degrees. Furthermore, evaluation was also performed visually. The visual evaluation results are shown in Table 3.

  As described above, the use of the optical compensation film of the present invention makes it easy to cope with changes in optical characteristics required for the compensation film due to cell design.

  According to the present invention, it is possible to provide a VA mode liquid crystal display device having excellent viewing angle characteristics.

It is a schematic sectional drawing of an example of the optical compensation sheet | seat of this invention. It is a schematic sectional drawing of an example of the polarizing plate of this invention. It is a schematic sectional drawing of 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 of Example 1 and Comparative Examples 1 and 2 with the direction of the optical axis in a layer. The incident angle dependency of luminance at the azimuth angle of 45 degrees of the liquid crystal display devices of Example 1 and Comparative Examples 1 and 2 is shown.

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 (17)

An optical compensation sheet having an alignment layer and an optically anisotropic layer in this order on a transparent support, the optically anisotropic layer comprising a liquid crystalline compound having at least one reactive group and at least one ultraviolet region A polymerization initiator having dichroism, a chiral agent, and a photosensitizer having no dichroism of 2.2 to 12.1% by mass relative to the polymerization initiator having dichroism. It is formed by curing a liquid crystal layer formed by applying and drying a solution for forming an optically anisotropic layer on the alignment layer,
The front retardation (Re) of the optically anisotropic layer is not 0, and the wavelength λ nm from the direction inclined + 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 light having a wavelength of λ nm is incident from the direction inclined by −40 ° with respect to the normal direction of the optical compensation sheet, with the retardation value measured by the incident light and the in-plane slow axis as the tilt axis (rotation axis) An optical compensation sheet characterized in that the measured retardation values are substantially equal. The optical compensation sheet according to claim 1, wherein the alignment layer is formed by applying and drying an alignment layer forming solution on the transparent support. The optical compensation sheet according to claim 2 , wherein the alignment layer forming solution contains a polymer having a reactive group in a side chain, or a monomer or oligomer having a reactive group. The optical compensation sheet according to claim 3 , wherein the alignment layer forming solution contains a modified polyvinyl alcohol having a reactive group in a side chain. The optical compensation sheet according to any one of claims 1 to 4 , wherein the liquid crystal compound has at least one ethylenically unsaturated group. The optical compensation sheet according to any one of claims 3 to 5 , wherein a reactive group of the liquid crystal compound can react with a reactive group of the alignment layer. The optical compensation sheet according to any one of claims 1 to 6 , wherein the transparent support is a cellulose-based or cycloolefin-based polymer. The optical compensation sheet according to any one of claims 1 to 7 , wherein the optically anisotropic layer is formed by irradiating the liquid crystal layer with polarized ultraviolet rays. The optical compensation sheet according to claim 8 , wherein the surface temperature of the liquid crystal layer is maintained in a range of 70 to 160 ° C. in the irradiation with polarized ultraviolet rays. The optical compensation sheet according to claim 8 or 9 , wherein the optically anisotropic layer exhibits a cholesteric phase before irradiation with polarized ultraviolet rays. The optical compensation sheet according to any one of claims 1 to 10 , wherein the liquid crystal compound is a rod-like liquid crystal compound. And the optical compensation sheet according to any one of claims 1 to 11 a polarizing plate having a polarizing film. The liquid crystal display device having a polarizing plate according to the optical compensation sheet or claim 12 according to any one of claims 1 to 11. The liquid crystal display device according to claim 13 , wherein the display mode is a VA mode. A method for producing an optical compensation sheet having an alignment layer and an optically anisotropic layer in this order on a transparent support,
The optically anisotropic layer includes a liquid crystalline compound having at least one reactive group, a polymerization initiator having dichroism in at least one ultraviolet region, a chiral agent, and a polymerization initiation having the dichroism. A liquid crystal layer formed by applying and drying an optically anisotropic layer forming solution containing 2.2 to 12.1% by mass of a photosensitizer having no dichroism with respect to the agent on the alignment layer A method for producing an optical compensation sheet that cures. The orientation layer and an optically anisotropic layer on a transparent support possess in this order, polymerization having dichroism at least one ultraviolet region with a liquid crystal compound having optically anisotropic layer at least one reactive group In the optical compensation sheet obtained by curing a liquid crystal layer formed by applying and drying a solution for forming an optically anisotropic layer having an initiator and a chiral agent on the alignment layer ,
Re / Re (40) of the optically anisotropic layer ,
By adding photosensitizers with no dichroic 2.2 to 12.1 wt% based on the polymerization initiator having the dichroic to the optically anisotropic layer forming solution, control (However, the Re / Re (40) is a direction tilted by + 40 ° with respect to the normal direction of the optical compensation sheet with the front retardation (Re) and the in-plane slow axis as the tilt axis (rotation axis)). To the retardation value (Re (40)) measured by incidence of light having a wavelength of λ nm). The method according to claim 16, wherein Re / Re (40) of the optically anisotropic layer of the optical compensation sheet is reduced.