JP2009230050A - Liquid crystal panel and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal panel having a high contrast ratio in a front direction. <P>SOLUTION: The liquid crystal panel includes: a liquid crystal cell; a first polarizer arranged on the viewing side of the liquid crystal cell; and a second polarizer arranged on the back light side of the liquid crystal cell. The driving mode of the liquid crystal cell is an OCB mode or an HAN mode, and the transmittance (T<SB>1</SB>) of the first polarizer is higher than the transmittance (T<SB>2</SB>) of the second polarizer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal panel and a liquid crystal display device. More specifically, the present invention relates to a liquid crystal panel and a liquid crystal display device including two polarizers having different transmittances.

A liquid crystal display device (LCD) is an element that displays characters and images using the electro-optical characteristics of liquid crystal molecules, and is widely used in mobile phones, notebook computers, liquid crystal televisions, and the like. An LCD usually includes a liquid crystal panel in which polarizers are arranged on both sides of a liquid crystal cell. For example, in the normally black method, a black image can be displayed when no voltage is applied (see, for example, Patent Document 1). ). In recent years, LCDs have been required to exhibit a high front-side contrast ratio that allows characters and images to be drawn more clearly as the definition becomes higher and the applications are diversified.
Japanese Patent No. 3648240

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a liquid crystal panel and a liquid crystal display device that exhibit a high contrast ratio in the front direction.

The liquid crystal panel of the present invention comprises a liquid crystal cell, a first polarizer disposed on the viewing side of the liquid crystal cell, and a second polarizer disposed on the backlight side of the liquid crystal cell, and the liquid crystal The driving mode of the cell is OCB mode or HAN mode, and the transmittance (T ₁ ) of the _first polarizer is larger than the transmittance (T ₂ ) of the _second polarizer.

In a preferred embodiment, the difference (ΔT = T ₁ −T ₂ ) between the transmittance (T ₁ ) of the first polarizer and the transmittance (T ₂ ) of the second polarizer is 0.1 to 0.1. 6.0%.

In a preferred embodiment, the transmittance (T ₁ ) of the first polarizer is 41.1 to 44.3%.

In a preferred embodiment, the transmittance (T ₂ ) of the second polarizer is 38.3 to 43.3%.

  In a preferred embodiment, the degree of polarization of the first polarizer and / or the second polarizer is 99% or more.

  In a preferred embodiment, the first polarizer and / or the second polarizer contain iodine.

In a preferred embodiment, the difference (ΔI = I ₂ −I ₁ ) between the iodine content (I ₂ ) of the _second polarizer and the iodine content (I ₁ ) of the first polarizer is 0. 1 to 2.6% by weight.

In a preferred embodiment, the iodine content (I ₁ ) of the first polarizer is 1.8 to 3.5% by weight.

In a preferred embodiment, the iodine content (I ₂ ) of the second polarizer is 2.3 to 5.0% by weight.

  In a preferred embodiment, the liquid crystal cell further includes a first retardation layer between the liquid crystal cell and the first polarizer, and the first retardation layer includes a first O plate, A second retardation layer is further provided between the second polarizer and the second retardation layer, and the second retardation layer includes a second O plate.

  In a preferred embodiment, the direction in which the optical axis direction of the first O plate and the second O plate is projected onto the liquid crystal cell surface is substantially the same as the alignment processing direction of the liquid crystal cell.

  In a preferred embodiment, an angle formed by the slow axis of the first O plate and the absorption axis of the first polarizer is substantially 45 °, and the slow axis of the second O plate The angle formed with the absorption axis of the second polarizer is substantially 45 °.

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

  In the liquid crystal panel and the liquid crystal display device of the present invention, by arranging two polarizers with adjusted transmittances on both sides of the liquid crystal cell, the contrast ratio in the front direction is remarkably high, and excellent display characteristics can be obtained. .

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

(Definition of terms and symbols)
The definitions of terms and symbols in this specification are as follows.
(1) Transmittance of Polarizer The transmittance (T) is a Y value obtained by correcting the visibility with a 2-degree visual field (C light source) of JlS Z 8701-1982.
(2) Refractive index (nx, ny, nz)
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximum (ie, the slow axis direction), “ny” is the direction perpendicular to the slow axis in the plane, and “nz” is the thickness direction. Refractive index.
(3) In-plane retardation value The in-plane retardation value (Re [λ]) refers to the in-plane retardation value of the film at 23 ° C. and wavelength λ (nm). Re [λ] is obtained by Re [λ] = (nx−ny) × d, where d (nm) is the thickness of the film.
(4) Thickness direction retardation value Thickness direction retardation value (Rth [λ]) refers to a retardation value in the thickness direction of the film at 23 ° C. and wavelength λ (nm). Re [λ] is obtained by Rth [λ] = (nx−nz) × d, where d (nm) is the thickness of the film.

A. Overall Configuration of Liquid Crystal Panel FIG. 1A is a schematic sectional view of a liquid crystal panel according to a preferred embodiment of the present invention. The liquid crystal panel 100 includes a liquid crystal cell 30, a first polarizer 10 disposed on the viewing side of the liquid crystal cell 30, and a second polarizer 20 disposed on the backlight side of the liquid crystal cell 30. FIG. 1B is a schematic cross-sectional view of a liquid crystal panel according to another preferred embodiment of the present invention. The liquid crystal panel 100 ′ includes a liquid crystal cell 30, a first polarizer 10 disposed on the viewing side of the liquid crystal cell 30, and a second polarizer 20 disposed on the backlight side of the liquid crystal cell 30. Further, the liquid crystal panel 100 ′ is disposed between the first retardation layer 40 disposed between the liquid crystal cell 30 and the first polarizer 10, and between the liquid crystal cell 30 and the second polarizer 20. And a second retardation layer 50.

  Although not shown, the liquid crystal panel of the present invention may include other optical members as necessary. As the other optical member, any appropriate optical member can be adopted depending on the purpose. Typically, a protective layer disposed on one side or both sides of the polarizer, and a surface treatment layer disposed on the opposite side of the protective layer from the side having the polarizer are exemplified. In addition to these, for example, a liquid crystal film, a light scattering film, a diffraction film, another retardation film, an isotropic film, and the like can be given. Further, practically, any appropriate adhesive layer is disposed between the members constituting the liquid crystal panel of the present invention.

  The first polarizer 10 and the second polarizer 20 are preferably arranged such that the absorption axis of the first polarizer and the absorption axis of the second polarizer are substantially orthogonal to each other. . In this specification, “substantially orthogonal” includes a case of 90 ° ± 3.0 °, preferably 90 ° ± 1.0 °, and more preferably 90 ° ± 0.5 °. The axial relationship of the retardation layer will be described in Section A-3.

A-1. Liquid Crystal Cell Any appropriate liquid crystal cell 30 can be adopted. Examples of the liquid crystal cell include an active matrix type using thin film transistors and a simple matrix type typified by a super twist nematic liquid crystal display device.

  The liquid crystal cell preferably includes a pair of substrates 31, 31 'and a liquid crystal layer 32 as a display medium sandwiched between the pair of substrates 31, 31'. One substrate (active matrix substrate) is provided with an active element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, and a scanning line for supplying a gate signal to the active element and a signal line for supplying a source signal. It has been. The other substrate (color filter substrate) is provided with a color filter. The color filter may be provided on the active matrix substrate. Alternatively, when an RGB three-color light source is used for the illumination means of the liquid crystal display device as in the field sequential method, the color filter can be omitted.

  The distance between the pair of substrates is controlled by a spacer. An alignment film subjected to alignment treatment is provided on the side of each substrate in contact with the liquid crystal layer. Examples of the alignment treatment include a rubbing method in which a polymer film such as polyimide is rubbed in one direction with a fiber such as nylon or polyester. For example, when the initial alignment of liquid crystal molecules is controlled by using a patterned transparent substrate and utilizing a fringe electric field, the alignment film can be omitted.

  The driving mode of the liquid crystal cell is preferably a bent nematic (OCB) mode or a hybrid alignment (HAN) mode. FIG. 2 is a schematic cross-sectional view illustrating the alignment state of liquid crystal molecules in the OCB mode. The OCB mode is a drive mode in which the liquid crystal layer 32 is configured by so-called bend alignment. As shown in FIG. 2 (c), the bend alignment has a substantially parallel angle (alignment angle) when the alignment of the nematic liquid crystal molecules is in the vicinity of the substrate, and the alignment plane increases toward the center of the liquid crystal layer. An alignment state that exhibits an angle perpendicular to the liquid crystal layer, gradually changes so as to be aligned with the opposing substrate surface as the distance from the center of the liquid crystal layer, and does not have a twisted structure throughout the liquid crystal layer. Such a bend orientation is formed as follows. As shown in FIG. 2A, in a state where no electric field or the like is applied (initial state), the liquid crystal molecules are substantially homogeneously aligned. However, the liquid crystal molecules have a pretilt angle, and the pretilt angle near the substrate is different from the pretilt angle near the opposite substrate. When a predetermined bias voltage (typically, 1.5 V to 1.9 V) is applied thereto (when a low voltage is applied), a splay orientation as shown in FIG. A transition to bend orientation as shown can be achieved. When a display voltage (typically 5 V to 7 V) is applied from the bend alignment state (when a high voltage is applied), the liquid crystal molecules rise almost perpendicularly to the substrate surface as shown in FIG. In the normally white display mode, light that has passed through the second polarizer 20 and entered the liquid crystal layer in the state of FIG. 2D when a high voltage is applied proceeds without changing the polarization direction. 1 is absorbed by the polarizer 10. Therefore, a dark state is displayed. When the display voltage is lowered, it can return to the bend alignment and return to the bright display by the alignment regulating force of the rubbing process. In addition, gradation display is possible by changing the display voltage to control the tilt of the liquid crystal molecules to change the transmitted light intensity from the polarizer. Since the liquid crystal display device including the OCB mode liquid crystal cell can switch the phase transition from the splay alignment state to the bend alignment state at a very high speed, the liquid crystal display device in other drive modes such as the TN mode and the IPS mode. Compared to the above, it has a feature of excellent moving image display characteristics. Note that an arrow X in FIG. 2 indicates an alignment treatment direction (rubbing direction). In the OCB mode, the pair of substrates are typically arranged such that the alignment treatment direction of one substrate 31 and the alignment treatment direction of the other substrate 31 ′ are substantially parallel. In this specification, “substantially parallel” includes the case of 0 ° ± 3.0 °, preferably 0 ° ± 1.0 °, more preferably 0 ° ± 0.5 °.

  The display mode of the OCB mode liquid crystal cell is either a normally white mode that takes a dark state (black display) when a high voltage is applied, or a normally black mode that takes a bright state (white display) when a high voltage is applied. Can also be adopted. A normally white mode is preferable. This is because a high contrast ratio can be obtained and black display uniformity can be excellent.

  The cell gap (interval between the pair of substrates) of the OCB mode liquid crystal cell is preferably 2 to 10 μm, more preferably 3 to 9 μm, and particularly preferably 4 to 8 μm. By setting within such a range, the response time can be shortened and good display characteristics can be obtained.

The nematic liquid crystal used in the OCB mode liquid crystal cell preferably has a positive dielectric anisotropy. Specific examples of nematic liquid crystals having positive dielectric anisotropy include those described in JP-A-9-176645. A commercially available nematic liquid crystal may be used as it is. Examples of commercially available nematic liquid crystals include trade name “ZLI-4535” and trade name “ZLI-1132” manufactured by Merck & Co., Inc. The difference between the ordinary light refractive index (no) and the extraordinary light refractive index (ne) of the nematic liquid crystal, that is, the birefringence (Δn _LC ) can be appropriately selected according to the response speed and transmittance of the liquid crystal. Δn _LC is preferably 0.05 to 0.30, more preferably 0.10 to 0.30, and particularly preferably 0.12 to 0.30.

  The pretilt angle of the nematic liquid crystal used in the OCB mode liquid crystal cell is preferably 1 to 20 °, more preferably 2 to 15 °, and particularly preferably 3 to 10 °. By setting to such a range, the response time can be shortened and good display characteristics can be obtained.

  In the OCB mode liquid crystal cell, Re [590] when a low voltage is applied (the state shown in FIG. 2C) is preferably 100 to 400 nm, more preferably 130 to 350 nm, and particularly preferably 260 to 300 nm. Rth [590] is preferably −200 to −600 nm, more preferably −240 to −480 nm, and particularly preferably −280 to −360 nm.

  In the OCB mode liquid crystal cell, Re [590] when a high voltage is applied (the state shown in FIG. 2D) is preferably 50 to 150 nm, more preferably 65 to 125 nm, and particularly preferably 80 to 100 nm. Rth [590] is preferably −300 to −1200 nm, more preferably −450 to −1000 nm, and particularly preferably −600 to −800 nm.

FIG. 3 is a schematic cross-sectional view illustrating the alignment state of liquid crystal molecules in the HAN mode. As shown in FIG. 3B, when no voltage is applied, the liquid crystal molecules are aligned parallel to the substrate in the vicinity of the substrate 31 ′, and the angle of inclination with respect to the substrate increases along the thickness direction of the liquid crystal cell 30. In the vicinity of the substrate 31, it is oriented perpendicular to the substrate. Therefore, both a nematic liquid crystal having positive dielectric anisotropy (Np liquid crystal) and a nematic liquid crystal having negative dielectric anisotropy (Nn liquid crystal) can be used. The inclination θ of the liquid crystal molecules when a voltage is applied is represented by the sum of the initial elastic deformation θ ₀ and the dielectric deformation φ. When an Np liquid crystal is used, an alignment state as shown in FIG. 3A is taken, and when an Nn liquid crystal is used, an alignment state as shown in FIG. 3C is taken. One of the performance characteristics of the HAN mode is that there is no threshold voltage. This is because the elastic deformation θ ₀ already exists when no voltage is applied. As a result, the electro-optic effect occurs at a very low voltage.

A-2. Polarizer In this specification, “polarizer” refers to a material that converts natural light or polarized light into linearly polarized light. Preferably, the polarizer has a function of separating incident light into two orthogonal polarization components, transmitting one polarization component, and absorbing, reflecting, and / or scattering the other polarization component. Arbitrary appropriate things can be employ | adopted for a polarizer (1st polarizer, 2nd polarizer).

The transmittance (T ₁ ) of the _first polarizer is larger than the transmittance (T ₂ ) of the second polarizer 20. By adopting such a configuration, the contrast ratio in the front direction can be remarkably improved. Thus, using two polarizers with adjusted transmittance on both sides of the liquid crystal cell, the contrast ratio in the front direction is greatly improved, which is a finding first found by the present inventors. This is an unexpected and excellent effect. The difference (ΔT = T ₂ −T ₁ ) between the transmittance (T ₂ ) of the _second polarizer and the transmittance (T ₁ ) of the first polarizer is preferably 0.1 to 6. It is 0%, more preferably 0.1 to 5.0%, particularly preferably 0.2 to 4.5%, and most preferably 0.3 to 4.2%. By using two polarizers having a transmittance difference in such a range, a liquid crystal display device having a still higher contrast ratio in the front direction can be obtained.

The transmittance (T ₁ ) of the first polarizer can be set to any appropriate value. It is preferably 41.1 to 44.3%, more preferably 41.5 to 44.3%, particularly preferably 41.9 to 44.2%, and most preferably 42.3 to 44.2%. It is. By setting T ₁ in such a range can further, the contrast ratio in the front direction is high liquid crystal display device obtained.

The transmittance (T ₂ ) of the second polarizer can be set to any appropriate value. It is preferably 38.3 to 43.3%, more preferably 38.6 to 43.2%, particularly preferably 39.9 to 43.1%, and most preferably 39.2 to 43.0%. It is. By setting T ₂ in such range may further, the contrast ratio in the front direction is high liquid crystal display device obtained.

  The transmittance of the polarizer can be adjusted by any appropriate method. Specific examples include a method of appropriately selecting a polarizer-containing component (for example, a method of adjusting the content of iodine in a polarizer containing a polyvinyl alcohol-based resin containing iodine). Details will be described later. In addition, commercially available polarizers (polarizing plates) having different transmittances can be appropriately selected and used as the first polarizer and the second polarizer.

  The degree of polarization (P) of the first polarizer and / or the second polarizer is preferably 99% or more, more preferably 99.5% or more, and particularly preferably 99.8%. By setting the degree of polarization (P) in such a range, a liquid crystal display device with a still higher contrast ratio in the front direction can be obtained.

The degree of polarization can be measured using a spectrophotometer [product name “DOT-3” manufactured by Murakami Color Research Laboratory Co., Ltd.]. As a specific method for measuring the degree of polarization, the parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the polarizer are measured, and the formula: degree of polarization (%) = {(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100. Here, the parallel transmittance (H ₀ ) is a value of the transmittance of a parallel laminated polarizer prepared by superposing two identical polarizers so that their absorption axes are parallel to each other. Further, the orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal laminated polarizer produced by superposing two identical polarizers so that their absorption axes are orthogonal to each other. In addition, these transmittance | permeability is Y value which performed visibility correction | amendment by the 2 degree visual field (C light source) of JlS Z 8701-1982.

  The thickness of the polarizer may be any appropriate value. Preferably it is 5-80 micrometers. It is because it can be excellent in mechanical strength.

  The polarizer can be usually obtained by stretching a polymer film containing a polyvinyl alcohol-based resin. Preferably, the polarizer contains iodine. Such a polarizer is excellent in optical characteristics.

  As described above, the transmittance of the polarizer can be adjusted by adjusting the content of iodine in the polarizer. Specifically, increasing the content of iodine in the polarizer can decrease the transmittance of the polarizer. On the other hand, if the iodine content in the polarizer is decreased, the transmittance of the polarizer can be increased. Note that this method can be applied to the production of a roll-shaped polarizing plate and the production of a sheet-like polarizing plate.

The relationship between the iodine content (I ₁ ) of the first polarizer and the iodine content (I ₂ ) of the second polarizer is preferably I ₂ > I ₁ . The difference (ΔI = I ₂ −I ₁ ) between the iodine content (I ₂ ) of the second polarizer and the iodine content (I ₁ ) of the first polarizer is preferably 0.1-2. It is 6% by weight, more preferably 0.1 to 2.0% by weight, particularly preferably 0.1 to 1.4% by weight, and most preferably 0.15 to 1.2% by weight. By setting the relationship between the iodine contents of the respective polarizers within such a range, the transmittance relationship within the above preferable range can be satisfied, and a liquid crystal display device with a higher contrast ratio in the front direction can be obtained.

  The iodine content of the first polarizer and / or the second polarizer is preferably 1.8 to 5.0% by weight, more preferably 2.0 to 4.0% by weight. The iodine content of the first polarizer is preferably 1.8 to 3.5% by weight, more preferably 1.9 to 3.2% by weight. The iodine content of the second polarizer is preferably 2.3 to 5.0% by weight, more preferably 2.5 to 4.5% by weight, particularly preferably 2.5 to 4.0% by weight. is there. By setting the iodine content of each polarizer in such a range, it is possible to obtain a polarizer having a transmittance in the above preferred range and to obtain a liquid crystal display device having a high contrast ratio in the front direction.

  Preferably, the first polarizer and / or the second polarizer further contain potassium. The potassium content is preferably 0.2 to 1.0% by weight, more preferably 0.3 to 0.9% by weight, and particularly preferably 0.4 to 0.8% by weight. By setting the potassium content in such a range, a polarizer having a transmittance in the above preferable range and having a high degree of polarization can be obtained.

  Preferably, the first polarizer and / or the second polarizer further contain boron. The boron content is preferably 0.5 to 3.0% by weight, more preferably 1.0 to 2.8% by weight, and particularly preferably 1.5 to 2.6% by weight. By setting the boron content in such a range, a polarizer having a transmittance in the above preferred range and a high degree of polarization can be obtained.

  The polyvinyl alcohol resin can be obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer. The saponification degree of the polyvinyl alcohol-based resin is preferably 95.0 to 99.9 mol%. The saponification degree can be determined according to JIS K 6726-1994. By using a polyvinyl alcohol resin having a saponification degree in such a range, a polarizer having excellent durability can be obtained.

  Any appropriate value can be selected as the average degree of polymerization of the polyvinyl alcohol resin according to the purpose. The average degree of polymerization is preferably 1200 to 3600. The average degree of polymerization can be determined according to JIS K 6726-1994.

  Any appropriate molding method can be adopted as a method for obtaining the polymer film containing the polyvinyl alcohol resin. As a shaping | molding processing method, the method of Unexamined-Japanese-Patent No. 2000-315144 [Example 1] is mentioned, for example.

  The polymer film containing the polyvinyl alcohol resin preferably contains a plasticizer and / or a surfactant. This is because the dyeability and stretchability of the polarizer can be further improved. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. The content of each of the plasticizer and the surfactant is preferably more than 1 and 10 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin.

  As the polymer film containing the polyvinyl alcohol resin, a commercially available film can be used as it is. As a polymer film containing a commercially available polyvinyl alcohol-based resin, for example, “Kuraray Vinylon Film” manufactured by Kuraray Co., Ltd., “Toselo Vinylon Film” manufactured by Tosero Co., Ltd., Nippon Synthetic Chemical Industry Co., Ltd. Product name “Nippon Vinylon Film” and the like.

  Arbitrary appropriate methods can be employ | adopted for the manufacturing method of the said polarizer. An example will be described with reference to FIG. FIG. 4 is a schematic view showing the concept of a typical production process of a polarizer used in the present invention. For example, the polymer film 301 containing a polyvinyl alcohol-based resin is drawn out from the feeding unit 300 and immersed in a swelling bath 310 containing pure water and a dyeing bath 320 containing an aqueous iodine solution, and rolls 311 and 312 having different speed ratios. Swelling treatment and dyeing treatment are performed while tension is applied in the longitudinal direction of the film at 321 and 322. Next, the film subjected to the swelling treatment and the dyeing treatment is immersed in the first crosslinking bath 330 containing potassium iodide and the second crosslinking bath 340, and is rolled with rolls 331, 332, 341 and 342 having different speed ratios. While tension is applied in the longitudinal direction of the film, a crosslinking treatment and a final stretching treatment are performed. The film subjected to the crosslinking treatment is immersed in a washing bath 350 containing pure water by rolls 351 and 352 and subjected to a washing treatment. The water-washed film is dried by the drying means 360, so that the moisture content is adjusted to, for example, 10% to 30%, and is wound by the winding unit 380. The polarizer 370 can be obtained by stretching a polymer film containing a polyvinyl alcohol resin 5 to 7 times the original length through these steps.

  In the dyeing step, the amount of iodine added to the dyeing bath for obtaining a polarizer having excellent optical properties is preferably 0.01 to 0.15 parts by weight, more preferably 0, per 100 parts by weight of water. 0.01 to 0.05 parts by weight. Increasing the amount of iodine added to the dyeing bath within the above range can result in a polarizer having low transmittance. Further, when the amount of iodine added to the dyeing bath is decreased within the above range, a polarizer having a high transmittance can be obtained as a result.

  The amount of potassium iodide added to the dyeing bath is preferably 0.05 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight with respect to 100 parts by weight of water. By setting the addition amount of potassium iodide in such a range, it is possible to obtain a polarizer having a transmittance in the above preferred range and a high degree of polarization.

  In the dyeing step, the amount of potassium iodide added to the first crosslinking bath and the second crosslinking bath for obtaining a polarizer having excellent optical properties is preferably about 0.1 parts by weight with respect to 100 parts by weight of water. 5 to 10 parts by weight, more preferably 1 to 7 parts by weight. The addition amount of boric acid in the first crosslinking bath and the second crosslinking bath is preferably 0.5 to 10 parts by weight, more preferably 1 to 7 parts by weight. By setting the addition amounts of potassium iodide and boric acid in such a range, a polarizer having a transmittance in the above preferable range and having a high degree of polarization can be obtained.

A-3. Retardation Layer The first retardation layer 40 and the second retardation layer 50 may employ a retardation layer having any appropriate optical characteristic. The first retardation layer 40 preferably includes a first O plate. The second retardation layer 50 preferably includes a second O plate. This is because a liquid crystal display device with a higher contrast ratio in the front direction can be obtained. Typically, the first retardation layer and the second retardation layer are a laminate of a substrate and an O plate. As the substrate, the same protective layer as described later can be adopted. When the retardation layer is directly laminated on the polarizer, the substrate can function as a protective layer.

  In this specification, the “O plate” refers to a retardation layer in which molecules are tilted. The thickness of the O plate is usually 0.1 to 10 μm, preferably 0.5 to 5 μm. Hereinafter, the O plate will be described.

  In one embodiment, the O plate is a solidified layer or a cured layer of a rod-like liquid crystal compound aligned in a hybrid arrangement.

In this specification, “hybrid alignment” refers to a state in which the tilt angle (tilt angle) of a liquid crystal compound increases or decreases continuously or intermittently in the thickness direction. That is, the tilt angle (θ _P ) on the polarizer side and the tilt angle (θ _B ) on the liquid crystal cell side are different. Here, the tilt angle (θ) represents an angle formed by the adjacent layer surface and the liquid crystal compound molecules, and the case where the molecules are arranged in parallel in the plane is defined as 0 °. FIG. 5 schematically shows a typical arrangement state of rod-like liquid crystal compound molecules in the hybrid arrangement. In addition, the liquid crystal compound tilt angle with respect to the adjacent interface is shown in Journal of Applied Phisics Vol. 4 as shown in the following formulas (I) and (II). 38 (1999) p. 748 to the pre-measured n _e , n _O , and phase difference values (in the direction parallel to the slow axis, polar angle −40 ° to + 40 ° (normal direction is 0 °)) Each value measured in 5 ° increments) can be substituted. Here, θ _air represents the tilt angle of one side (for example, air interface) of the liquid crystal compound, and θ _AL represents the tilt angle of the other side (for example, substrate or alignment film) interface. d represents the thickness of the solidified layer or hardened layer of the liquid crystal compound aligned in a hybrid arrangement. n _e represents an extraordinary refractive index of the liquid crystal compounds, n _O represents an ordinary refractive index of the liquid crystal compound.

  In the present specification, the “rod-like liquid crystal compound” has a mesogenic group in the molecular structure, and the refractive index in the major axis direction of the mesogenic group is larger than that in the minor axis direction. A compound that exhibits a liquid crystal phase due to a change in temperature or the action of a certain amount of solvent. The “solidified layer” refers to a liquid crystal composition that has been softened, melted, or in a solution state, cooled and solidified. The “cured layer” refers to a liquid crystal composition in which a part or all of the liquid crystalline composition is crosslinked by heat, catalyst, light and / or radiation to be insoluble or hardly soluble. “Liquid crystal composition” refers to a liquid crystal compound that exhibits a liquid crystal phase and exhibits liquid crystal properties. However, the liquid crystal composition exhibits liquid crystallinity before film formation, but after film formation, for example, a network structure may be formed by photopolymerization or the like, and may not exhibit liquid crystallinity.

  The rod-like liquid crystal compound preferably exhibits a crystalline or glass state at room temperature and develops a nematic liquid crystal phase at a high temperature. When such a rod-like liquid crystal compound is used, for example, after forming a hybrid arrangement in a state showing a liquid crystal phase, the arrangement state can be fixed by cooling or crosslinking.

  The mesogenic group is a constituent part necessary for forming a liquid crystal phase and usually contains a cyclic unit. Specific examples of the cyclic unit include biphenyl group, phenylbenzoate group, phenylcyclohexane group, azoxybenzene group, azomethine group, azobenzene group, phenylpyrimidine group, diphenylacetylene group, diphenylbenzoate group, bicyclohexane group, cyclohexylbenzene group, A terphenyl group etc. are mentioned. Among these, a biphenyl group and a phenylbenzoate group are preferable. Moreover, these cyclic units may have a substituent at the terminal. Examples of the substituent include a cyano group, an alkyl group, an alkoxy group, and a halogen group.

  The rod-like liquid crystal compound may be a polymer substance (polymer liquid crystal) having a mesogen group in the main chain and / or side chain, or a low molecular substance (low molecule liquid crystal) having a mesogen group in a part of the molecular structure. It may be. The polymer liquid crystal is characterized by high film forming productivity because it can be cooled from the liquid crystal state to fix the molecular alignment state. Since the low-molecular liquid crystal is excellent in orientation, it has a feature that a highly transparent retardation layer is easily obtained.

  The rod-like liquid crystal compound preferably has at least one crosslinkable functional group in a part of the molecular structure. This is because the cross-linking reaction increases the mechanical strength and provides a retardation layer having excellent durability. Examples of the crosslinkable functional group include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl ether group. As the rod-like liquid crystal compound, a commercially available product can be used as it is. As a commercially available rod-shaped liquid crystal compound having a crosslinkable functional group, for example, trade name “Paliocolor LC242” manufactured by BASF, trade name “CB483” manufactured by HUNTSMAN, and the like can be given. In addition to the commercially available product or the synthesized rod-like liquid crystal compound, the liquid crystalline composition may contain other liquid crystal compounds and arbitrary additives such as a polymerization initiator and a leveling agent.

Any appropriate method can be adopted as a method of forming the O plate. As one embodiment, a method including the following steps A _{1 to} E ₁ can be mentioned.
(A ₁ ) Step of preparing two substrates, performing a first alignment process on one side of one substrate, and performing a second alignment process on one side of the other substrate (however, the first alignment process and the first alignment process) The orientation treatments of the two are not identical.
(B ₁ ) a step of preparing a coating liquid containing a rod-like liquid crystal compound and a solvent;
(C ₁ ) A step of forming a laminate by sandwiching the coating liquid between the two substrates in a state where the alignment treatment surfaces of the two substrates are opposed to each other;
(D ₁₎ heating the laminate to the liquid crystal temperature range;
(E ₁₎ step of cooling the laminate below the liquid crystal temperature range.
Here, the first alignment process and the second alignment process are each independently a vertical alignment process, a horizontal alignment process, or a tilt alignment process.

Another embodiment of the method for forming the O plate includes a method including the following steps A _{2 to} E ₂ .
(A ₂ ) A step of performing an alignment treatment on the substrate;
(B ₂₎ preparing a coating solution containing a rod-like liquid crystal compound and a solvent;
(C ₂ ) A step of applying the coating solution to the surface of the substrate that has been subjected to the orientation treatment to form a laminate.
(D ₂₎ step above with the coating liquid substrate side of that in the state in which the interface on the side opposite the contact with the air, to heat the laminate to the liquid crystal temperature range;
(E ₂₎ step of the laminate to cool to below the liquid crystal temperature range.
Here, the alignment treatment is vertical alignment treatment or inclined alignment treatment. Which to select can be appropriately determined according to the type and chemical properties of the rod-like liquid crystal compound to be used.

The tilt angle (θ _P ) on the polarizer side and the tilt angle (θ _B ) on the liquid crystal cell side of the rod-shaped liquid crystal compound are, for example, the conditions of the above steps A _{1 to} E ₁ or steps A _{2 to} E ₂ , It can adjust by selecting the kind of a compound or a liquid crystalline composition suitably.

  Any appropriate method can be adopted as the alignment treatment method. For example, a method of forming an alignment agent layer (alignment film) by adsorbing an alignment agent on the surface of the substrate; a method of changing the shape of the substrate or the surface of the alignment film formed on the substrate; Examples include a method of irradiating light on the surface of the formed alignment film (photo-alignment method). Among these, the photo-alignment method is preferable. Since the photo-alignment method is a process in which generation of static electricity, dust, dust, and the like is extremely small, a retardation layer with excellent quality can be produced. Furthermore, the tilt angle of the rod-like liquid crystal compound in the retardation layer and the slow axis direction in the retardation layer plane can be controlled by appropriately selecting the direction and orientation of light irradiation.

  Examples of the alignment agent for the vertical alignment treatment include lecithin, versamide 100, octadecylmalonic acid, organic silane, tetrafluoroethylene, polyimide, stearic acid, and the like. Examples of the alignment agent for the horizontal alignment treatment include carbon, polyoxyethylene, versamide 125, polyvinyl alcohol, polyimide, dibasic carboxylic acid chromium complex, organic silane, acetylene, dibasic fatty acid, and crown ether. It is done.

  The alignment agent for the photo-alignment method (the formed film is also referred to as a photo-alignment film) preferably contains a compound having at least one photoreactive functional group in the molecular structure. Examples of the photoreaction include photoisomerization reaction, photoring opening reaction, photodimerization reaction, photolysis reaction, and photofleece transfer reaction. Examples of the photoreactive functional group that causes the photoisomerization reaction include an azobenzene group, a stilbene group, an α-hydrazono-β-ketoester group, a cinnamate group, a benzylidenephthalimidine group, and retinoic acid. Examples of the photoreactive functional group that causes a photodimerization reaction include a cinnamate group, a benzylidenephthalimidine group, a chalcone group, a coumarin group, a stilpyridine group, and an anthracene group.

As a condition for irradiating light on the surface of the alignment film (photo-alignment film), for example, any appropriate method can be adopted depending on the type of the photochemical reaction. Examples of the light source for light irradiation include an ultra high pressure mercury lamp, a flash UV lamp, a high pressure mercury lamp, a low pressure mercury lamp, a deep UV lamp, a xenon lamp, and a metal halide lamp. The wavelength of the light source is preferably 210 to 380 nm. In addition, it is preferable to cut and irradiate a 100-200 nm wavelength range with a filter etc. This is because the photodecomposition reaction of the photo-alignment film can be suppressed. The value of the light irradiation amount measured at a wavelength of 365 nm is preferably 5 to 500 mJ / cm ² . Under such conditions, the rod-like liquid crystal compound can be uniformly aligned in a hybrid arrangement.

  Arbitrary appropriate methods can be employ | adopted for the method of preparing the coating liquid containing the said rod-shaped liquid crystal compound and a solvent. Here, the “coating liquid” refers to a solution or a dispersion. Examples of the solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pentanone, 2-hexanone, diethyl ether, tetrahydrofuran, dioxane, anisole, ethyl acetate, butyl acetate, toluene, xylene, chloroform, dichloromethane, Examples include dichloroethane, dimethylformamide, dimethylacetamide, methyl cellosolve and the like. These may be used alone or in admixture of two or more. The concentration of the rod-like liquid crystal compound is preferably 5 to 40% by weight.

  As the coating method of the coating liquid, a coating method using any appropriate coater can be adopted. As the coater, for example, reverse roll coater, forward rotation roll coater, gravure coater, knife coater, rod coater, slot die coater, slot orifice coater, curtain coater, fountain coater, air doctor coater, kiss coater, dip coater, bead coater, blade coater, Examples include cast coaters, spray coaters, spin coaters, extrusion coaters, and hot melt coaters. A reverse roll coater, a normal rotation roll coater, a gravure coater, a rod coater, a slot die coater, a slot orifice coater, a curtain coater and a fountain coater are preferable. This is because a solidified layer having a small thickness variation can be obtained. The coater preferably uses a coater head using a closed applicator in order to prevent a change in the concentration of the coating solution.

Any appropriate method can be adopted as a method of forming the solidified layer. Examples of the method for forming the solidified layer include a method including the steps A _{1 to} E ₁ and a method including the steps A _{2 to} E ₂ . The heating temperature in the step _{D 1} or step _{D 2} is preferably 30 ° C. or higher, the liquid crystal phase - a or less isotropic phase transition temperature (Ti), more preferably from 30 to 120 ° C.. As the heating means, for example, an air circulation type drying oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, a roll heated for temperature control, a heat pipe roll or a metal belt is used. Method and temperature control method. The heat drying time (drying time) is usually 1 to 20 minutes. The isotropic phase transition temperature (Ti) can be determined by observing a sample of a liquid crystal compound or a liquid crystalline composition with a polarizing microscope.

Arbitrary appropriate methods can be employ | adopted for the method of forming the said hardened layer. Preferably, as the rod-like liquid crystal compound, a cross-linkable rod-like liquid crystal compound having at least one cross-linkable functional group in a part of the molecular structure is used, and this is irradiated with ultraviolet rays for photocrosslinking. In this case, the ultraviolet irradiation is preferably performed after the solidified layer is formed or in the course of solidification. As the ultraviolet irradiation condition, for example, any appropriate condition can be selected according to the type of photochemical reaction of the crosslinkable functional group. As the light irradiation light source, a light source similar to the light source exemplified in the photo-alignment method can be adopted. The wavelength of the light source is preferably 210 to 380 nm. In addition, it is preferable to cut and irradiate a 100-200 nm wavelength range with a filter etc. This is because the photodecomposition reaction of the alignment film and the rod-like liquid crystal compound can be suppressed. The value of the light irradiation amount measured at a wavelength of 310 nm is preferably 30 to 1000 mJ / cm ² . Furthermore, it is preferable to replace the atmosphere around the crosslinkable rod-like liquid crystal compound or the crosslinkable composition containing the same with an inert gas such as nitrogen. If it is such conditions, the hardened layer excellent in thickness uniformity can be formed.

  In another embodiment, the O plate is a solidified layer or a hardened layer of a disk-like liquid crystal compound aligned in a hybrid arrangement. In the present specification, the “disk-shaped liquid crystal compound” is a molecule having a disk-shaped core, and means a liquid crystal molecule exhibiting a disk phase and / or a discotic nematic phase.

  The disk-shaped liquid crystal compound is usually a molecule in which 2 to 8 side chains are bonded radially to the disk-shaped central core through ether bonds or ester bonds. As the central core, “Liquid Crystal Dictionary” (1989) p. 22 Examples thereof include benzene, triphenylene, turxene, pyran, lupigarol, porphyrin, metal complex and the like as described in FIG. The discotic liquid crystal compound is preferably a triphenylene-based discotic compound having triphenylene as a central core, and more preferably a liquid crystal compound represented by the following general formula (1).

  N in the general formula (1) is an integer of 2 to 10. n is preferably 4-8, particularly preferably 4-6, and most preferably 6.

Any appropriate method can be adopted as a method of forming the O plate using the discotic liquid crystal compound. For example, a method comprising the step _A 3 -C ₃ below.
(A ₃ ) A step of performing an alignment treatment on the surface of the substrate (support);
(B ₃ ) a step of applying a solution or dispersion of a liquid crystalline composition containing a discotic liquid crystal compound to the orientation-treated surface and tilting and orienting the discotic liquid crystal compound;
(C ₃ ) A step of drying the liquid crystalline composition to form a solidified layer.

The curing layer, in addition to the above Step A ₃ -C _3, can be obtained by a process comprising the step D ₃ below.
(D ₃ ) A step of curing the liquid crystalline composition by irradiating the solidified layer obtained in the step C ₃ with ultraviolet rays. When obtaining a cured layer, the discotic liquid crystal compound is photocrosslinkable. It is preferable to add a photocrosslinkable compound to the liquid crystalline composition.

  Any appropriate alignment treatment method can be adopted as the method for inclining alignment of the discotic liquid crystal compound. Examples of the alignment treatment method include an oblique vapor deposition method, a photo alignment method, and a rubbing method. The oblique deposition method is typically a method in which an oxide such as silicon oxide is deposited from an oblique direction with respect to a substrate. In this method, the tilt angle of liquid crystal molecules can be adjusted by appropriately selecting the deposition angle, the number of depositions, and the like. The photo-alignment method is described in, for example, CMC Publishing “Functional Materials” Vol. 25No. 12 (2005) p. 15-P. 21 is a method in which a photoreactive alignment film formed on a substrate surface is irradiated with polarized light or non-polarized light from an oblique direction. In this method, the tilt angle of liquid crystal molecules can be adjusted by appropriately selecting the irradiation angle, irradiation time, etc. of polarized light or non-polarized light. The rubbing method is a method in which the substrate or the alignment film surface is rubbed in one direction with cotton cloth, nylon, rayon or the like.

  In addition, regarding the calculation method of the tilt angle of the discotic liquid crystal compound, the alignment treatment method, the preparation method of the coating liquid, and the like, the same method as that described for the rod-shaped liquid crystal compound can be employed.

The direction in which the optical axis direction of the first O plate is projected onto the liquid crystal cell surface (also referred to as an alignment direction) is preferably substantially the same as the alignment treatment direction of the liquid crystal cell. The direction in which the optical axis direction of the second O plate is projected onto the liquid crystal cell surface is preferably substantially the same as the alignment processing direction of the liquid crystal cell. In this specification, the “optical axis direction” refers to the orientation of the entire liquid crystal molecules as viewed statistically. The optical axis direction of the O plate refers to the direction of the optical axis when the O plate is formed of a liquid crystal compound that is uniformly aligned in the thickness direction (that is, when the O plate has an optical axis). On the other hand, when the O plate is formed of a liquid crystal compound that is non-uniformly oriented in the thickness direction (for example, a hybrid alignment) (that is, when the optical axis is not present in the O plate), it refers to the direction of the average inclination angle. . The average tilt angle is θ _ave. = (Θ _P + θ _B ) / 2, and the θ _ave. Is projected in-plane to the slow axis of the O plate.

The average inclination angle (θ _ave. ) Is preferably 10 to 45 °, more preferably 15 to 42 °, and particularly preferably 20 to 40 °. By setting the average tilt angle in such a range, more appropriate optical compensation is performed, and a liquid crystal display device having a high contrast ratio in an oblique direction can be obtained.

  The angle formed by the slow axis of the first O plate and the absorption axis of the first polarizer is substantially 45 °. The angle formed by the slow axis of the second O plate and the absorption axis of the second polarizer is substantially 45 °. Here, “substantially 45 °” includes the case of 45 ° ± 3.0 °, preferably 45 ° ± 1.0 °, and more preferably 45 ° ± 0.5 °. By arranging in such an axial relationship, more appropriate optical compensation of the liquid crystal cell is performed, and a liquid crystal display device having a high contrast ratio in an oblique direction can be obtained.

  The direction in which the optical axis direction of the O plate is projected onto the liquid crystal cell surface and the slow axis direction of the O plate are substantially the same. Further, when the retardation layer is a laminate of the O plate and the substrate and the in-plane retardation value of the substrate is substantially zero, the in-plane retardation value and retardation of the retardation layer and the O plate are substantially zero. The phase axis directions are substantially the same.

  The transmittance (T [590]) at a wavelength of 590 nm of the O plate is preferably 85% or more, more preferably 90% or more.

  The in-plane retardation value (Re [590]) at a wavelength of 590 nm of the O plate is the phase difference of the liquid crystal cell during black display (when voltage is applied) when the display mode of the liquid crystal cell is a normally white mode. It can be set to be substantially equal to the value. In the present invention, Re [590] of the O plate (the first retardation layer and the second retardation layer) is preferably 50 to 150 nm, more preferably 65 to 125 nm, and particularly preferably 80 to 100 nm. By setting the in-plane retardation value in such a range, more appropriate optical compensation is performed, and a liquid crystal display device having a high contrast ratio in an oblique direction can be obtained.

A-4. Others The protective layer is used, for example, to prevent the polarizer from contracting or expanding, or to prevent deterioration due to ultraviolet rays. Further, it may have a function of expanding the viewing angle of the liquid crystal cell. That is, it can function as an optical compensation layer. Any appropriate layer can be adopted as the protective layer. The thickness of the protective layer is preferably 20 to 100 μm. The transmittance (T [590]) at a wavelength of 590 nm of the protective layer is preferably 90% or more.

  Any appropriate material can be adopted as a material for forming the protective layer. Preferably, the protective layer is a polymer film containing a cellulose resin, a norbornene resin, or an acrylic resin. As a polymer film containing a cellulose resin, for example, it can be obtained by the method described in Example 1 of JP-A-7-112446. As a polymer film containing a norbornene resin, for example, it can be obtained by the method described in JP-A-2001-350017. As a polymer film containing an acrylic resin, for example, it can be obtained by the method described in Example 1 of JP-A-2004-19892.

  The protective layer may be subjected to any appropriate surface treatment on the surface. For example, as the protective layer, a commercially available polymer film subjected to surface treatment can be used as it is. Alternatively, a commercially available polymer film can be used after any surface treatment. Examples of the surface treatment include diffusion treatment (antiglare treatment), antireflection treatment (antireflection treatment), hard coat treatment, and antistatic treatment. Examples of commercially available diffusion-treated (antiglare-treated) products include AG150, AGS1, AGS2, and AGT1 manufactured by Nitto Denko Corporation. Examples of commercially available antireflection treatment (anti-reflection treatment) products include ARS and ARC manufactured by Nitto Denko Corporation. Examples of the commercially available film subjected to the hard coat treatment and the antistatic treatment include “KC8UX-HA” manufactured by Konica Minolta Opto Co., Ltd.

  Any appropriate layer can be adopted as the surface treatment layer depending on the purpose. Examples thereof include a hard coat treatment layer, an antistatic treatment layer, an antireflection treatment (also referred to as antireflection treatment) layer, and a diffusion treatment (also referred to as antiglare treatment) layer. These surface treatment layers are used for the purpose of preventing the screen from being soiled or damaged, or preventing the display image from becoming difficult to see due to the reflection of indoor fluorescent light or sunlight on the screen. The surface treatment layer is generally formed by fixing the treatment agent for forming each treatment layer on the surface of the base film. The base film may also serve as the protective layer. Furthermore, the surface treatment layer may have a multilayer structure in which, for example, a hard coat treatment layer is laminated on the antistatic treatment layer. Examples of the commercially available surface treatment layer that has been subjected to the antireflection treatment include ReaLook series manufactured by NOF Corporation.

A-5. Lamination method Arbitrary appropriate methods can be employ | adopted as a lamination | stacking method of each structural member of the said liquid crystal panel. When the retardation layer is provided, preferably, a retardation layer, the polarizer, and a protective layer, if necessary, are laminated in advance to prepare a polarizing plate with a retardation layer, and the retardation layer is attached. The method of laminating | stacking a polarizing plate and a liquid crystal cell is mentioned. Each of the above layers is laminated via any appropriate adhesive layer (pressure-sensitive adhesive layer or adhesive layer). A typical example of the adhesive forming the adhesive layer is a polyvinyl alcohol-based adhesive. A typical example of the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive.

B. Liquid crystal display device The liquid crystal display device of this invention is equipped with the said liquid crystal panel. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. The liquid crystal display device 200 includes a liquid crystal panel 100 and a backlight unit 80 disposed on one side of the liquid crystal panel. In FIG. 6, the backlight unit 80 shows a case where a direct method is adopted, but a sidelight method may be adopted, for example.

  As in the illustrated example, when the direct method is employed, the backlight unit 80 includes a light source 81, a reflection film 82, a diffusion plate 83, a prism sheet 84, and a brightness enhancement film 85. In the case of adopting the sidelight system, the backlight unit preferably includes a light guide plate and a light reflector in addition to the above configuration. Note that some of the optical members illustrated in FIG. 6 may be omitted depending on the application, such as the illumination method of the liquid crystal display device and the driving mode of the liquid crystal cell, or may be replaced with other optical members.

  The liquid crystal display device may be a transmissive type that irradiates light from the back side of the liquid crystal panel to view the screen, or a reflective type that irradiates light from the viewing side of the liquid crystal panel to view the screen. good. Alternatively, the liquid crystal display device may be a transflective type having both transmissive and reflective properties.

  The liquid crystal display device of the present invention is used for any appropriate application. Applications include, for example, OA equipment such as personal computer monitors, notebook computers, and copiers, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable devices such as portable game machines, video cameras, televisions, microwave ovens, etc. Home appliances, back monitors, car navigation system monitors, car audio and other in-vehicle equipment, exhibition equipment such as commercial store information monitors, security equipment such as surveillance monitors, nursing care monitors, medical monitors, etc. Nursing care / medical equipment.

  Preferably, the use of the liquid crystal display device of the present invention is a television. The screen size of the television is preferably a wide 17 type (373 mm × 224 mm) or more, more preferably a wide 23 type (499 mm × 300 mm) or more, and particularly preferably a wide 32 type (687 mm × 412 mm) or more. .

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, each analysis method used in the Example is as follows.
(1) Transmittance of Polarizer The transmittance (T) is a Y value obtained by correcting the visibility with a 2-degree visual field (C light source) of JlS Z 8701-1982.
(2) Measuring method of phase difference values (Re [λ], Rth [λ]), Nz coefficient and T [590] Using a product name “KOBRA21-ADH” manufactured by Oji Scientific Instruments, at 23 ° C. It was measured. In addition, the value measured using the Abbe refractometer [Atago Co., Ltd. product name "DR-M4"] was used for the average refractive index.
(3) Method for Measuring Tilt Angle at Interface of Liquid Crystal Compound In the above formulas (I) and (II), n _e , n _O and phase difference value (polar angle −40 ° to + 40 ° in the direction parallel to the slow axis) It was determined by substituting (each value measured in increments of 5 °) into (normal direction is 0 °). The phase difference value was a value measured at a wavelength of 590 nm and 23 ° C. using a spectroscopic ellipsometer [manufactured by JASCO Corporation, product name “M-220”]. n _e and _{n O} is Abbe refractometer Atago Co., Ltd., trade name "DR-M4"] using the value measured using a.
(4) Measuring method of thickness When thickness was less than 10 micrometers, it measured using the spectrophotometer for thin films [Otsuka Electronics Co., Ltd. product name "instant multiphotometry system MCPD-2000"]. When the thickness was 10 μm or more, it was measured using a digital micrometer “KC-351C type” manufactured by Anritsu.
(5) Method for measuring contrast ratio of liquid crystal display device After 30 minutes have passed since the backlight was turned on in a dark room at 23 ° C., a white image and a black image were obtained using a product name “EZ Contrast 160D” manufactured by ELDIM. The Y value of the XYZ display system in the front direction when displayed was measured. The contrast ratio “YW / YB” in the front direction was calculated from the Y value (YW: white luminance) in the white image and the Y value (YB: black luminance) in the black image.

(Preparation of polarizer A)
A polymer film (trade name “VF-PS # 7500” manufactured by Kuraray Co., Ltd.) having a 75 μm-thick polyvinyl alcohol resin as a main component is placed in 5 baths under the following conditions (1) to (5) in the longitudinal direction of the film. The film was immersed while applying tension, and stretched so that the final stretching ratio was 6.2 times the original film length. The stretched film was dried in an air circulation drying oven at 40 ° C. for 1 minute to produce a polarizer A.
<Conditions>
(1) Swelling bath: 30 ° C. pure water.
(2) Dyeing bath: An aqueous solution at 30 ° C. containing 0.025 parts by weight of iodine with respect to 100 parts by weight of water and 0.2 parts by weight of potassium iodide with respect to 100 parts by weight of water.
(3) First crosslinking bath: 40 ° C. aqueous solution containing 3% by weight potassium iodide and 3% by weight boric acid.
(4) Second crosslinking bath: 60 ° C. aqueous solution containing 5% by weight potassium iodide and 4% by weight boric acid.
(5) Washing bath: 25 ° C. aqueous solution containing 3% by weight of potassium iodide.
The thickness of the polarizer A was 30 μm, the transmittance was 42.764%, and the degree of polarization was 99.96%. Moreover, the iodine content of the polarizer A was 2.06% by weight, the potassium content was 0.52% by weight, and the boron content was 2% by weight.

(Preparation of polarizer B)
Polarizer B was produced under the same conditions and method as for polarizer A, except that the amount of iodine added to the dyeing bath under the above condition (2) was 0.030 part by weight with respect to 100 parts by weight of water.
The thickness of the polarizer B was 30 μm, the transmittance was 41.786%, and the degree of polarization was 99.96%. Moreover, the iodine content of the polarizer A was 2.82 wt%, the potassium content was 0.64 wt%, and the boron content was 2 wt%.

(Retardation layer)
A product name “WVP219” manufactured by Fuji Film Co., Ltd. was used as the retardation layer. This film is a laminate of a substrate (a polymer film containing triacetyl cellulose) and an O plate.

(Liquid crystal cell)
Take out the liquid crystal panel from a commercially available liquid crystal display device (manufactured by Nanao, 23-inch liquid crystal television, trade name “VT23XD1”) including the liquid crystal cell in the OCB mode, and all the optical films such as polarizing plates arranged above and below the liquid crystal cell. Removed. The front and back of the glass plate of this liquid crystal cell were washed to obtain a liquid crystal cell.

(Preparation of polarizing plate A with retardation layer)
Polymer film containing cellulose resin having a thickness of 80 μm on one side of the polarizer A (trade name “ZRF80S” manufactured by Fuji Photo Film Co., Ltd .; Re [590] = 0.1 nm, Rth [590] = 1 nm) Was pasted through a water-soluble adhesive (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOHSEIMER Z200”) mainly composed of a polyvinyl alcohol-based resin.
The retardation layer was attached to the other side of the polarizer A via a water-soluble adhesive (trade name “Gosefimer Z200”). At this time, the O plate (retardation layer) was attached so that the slow axis was 45 ° with respect to the absorption axis of the polarizer A. Moreover, it stuck so that the board | substrate of retardation layer might become the polarizer A side. In this way, a polarizing plate A with a retardation layer was produced.

(Preparation of polarizing plate B with retardation layer)
A polarizing plate B with a retardation layer was produced in the same manner as the polarizing plate A with a retardation layer except that the polarizer B was used instead of the polarizer A.

[Example 1]
(Production of liquid crystal panel)
The polarizing plate A with a retardation layer was laminated on the viewing side of the liquid crystal cell via an acrylic pressure-sensitive adhesive (thickness 20 μm). At this time, the O plate (retardation layer) was laminated so that the slow axis direction was parallel to the alignment treatment direction of the liquid crystal cell.
Next, the polarizing plate B with retardation layer was laminated on the backlight side of the liquid crystal cell via an acrylic pressure-sensitive adhesive (thickness 20 μm). At this time, the O plate (retardation layer) was laminated so that the slow axis direction was parallel to the alignment treatment direction of the liquid crystal cell. The polarizer A and the polarizer B were laminated so that the absorption axis of the polarizer A and the absorption axis of the polarizer B were orthogonal to each other. In this way, a liquid crystal panel was produced. The slow axis of the retardation layer on the viewing side, the alignment treatment direction of the liquid crystal cell, the slow axis of the retardation layer on the backlight side, and the absorption axis of the polarizer (polarizer B) on the backlight side are respectively When the absorption axis of the viewing side polarizer (polarizer A) was 0 °, they were 45 °, 45 °, 45 °, and 90 ° counterclockwise.

(Production of liquid crystal display device)
The liquid crystal panel obtained above was combined with the backlight unit of the original liquid crystal display device to produce a liquid crystal display device.
After 30 minutes had passed since the backlight was lit, the white luminance and black luminance in the front direction of the liquid crystal display device were measured to obtain the contrast ratio. The results are shown in Table 1 together with the configuration of the liquid crystal panel.

(Comparative Example 1)
A liquid crystal panel and a liquid crystal display device were obtained in the same manner as in Example 1 except that the polarizing plate A with retardation layer was disposed instead of the polarizing plate B with retardation layer on the backlight side of the liquid crystal cell.

(Comparative Example 2)
A polarizing plate B with a retardation layer is disposed instead of the polarizing plate A with a retardation layer on the viewing side of the liquid crystal cell, and a polarizing plate B with a retardation layer is provided on the backlight side of the liquid crystal cell. A liquid crystal panel and a liquid crystal display device were obtained in the same manner as in Example 1 except that the polarizing plate A with retardation layer was disposed.

(Comparative Example 3)
A liquid crystal panel and a liquid crystal display device were obtained in the same manner as in Example 1 except that the polarizing plate B with retardation layer was disposed instead of the polarizing plate A with retardation layer on the viewing side of the liquid crystal cell.

As is apparent from Table 1, Example 1 has a significantly higher front-side contrast ratio than Comparative Examples 1 to 3. From this, by making the transmittance (T ₁ ) of the _first polarizing plate (viewing side) larger than the transmittance (T ₂ ) of the second polarizing plate (backlight side), the contrast ratio in the front direction is increased. Therefore, it can be said that a liquid crystal panel and a liquid crystal display device exhibiting excellent display characteristics can be obtained.

  As described above, the liquid crystal panel and the liquid crystal display device of the present invention show a high contrast ratio in the front direction, and are extremely useful for improving the display characteristics of, for example, a personal computer monitor and a liquid crystal television.

(A) is a schematic sectional drawing of the liquid crystal panel by preferable embodiment of this invention, (b) is a schematic sectional drawing of the liquid crystal panel by another preferable embodiment of this invention. It is a schematic sectional drawing explaining the orientation state of the liquid crystal molecule in OCB mode. It is a schematic sectional drawing explaining the orientation state of the liquid crystal molecule in HAN mode. It is a schematic diagram which shows the concept of the typical manufacturing process of a polarizer. It is a schematic diagram explaining the typical arrangement | sequence state of the rod-shaped liquid crystal compound molecule | numerator in a hybrid arrangement | sequence. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st polarizer 20 2nd polarizer 30 Liquid crystal cell 100 Liquid crystal panel

Claims (13)

A liquid crystal cell;
A first polarizer disposed on the viewing side of the liquid crystal cell;
A second polarizer disposed on the backlight side of the liquid crystal cell,
The driving mode of the liquid crystal cell is OCB mode or HAN mode,
The liquid crystal panel in which the transmittance (T ₁ ) of the _first polarizer is larger than the transmittance (T ₂ ) of the second polarizer. The difference (ΔT = T ₁ −T ₂ ) between the transmittance (T ₁ ) of the first polarizer and the transmittance (T ₂ ) of the second polarizer is 0.1 to 6.0%. The liquid crystal panel according to claim 1. 3. The liquid crystal panel according to claim 1, wherein the transmittance (T ₁ ) of the first polarizer is 41.1 to 44.3%. 4. The liquid crystal panel according to claim 1, wherein the transmittance (T ₂ ) of the second polarizer is 38.3 to 43.3%.   5. The liquid crystal panel according to claim 1, wherein a degree of polarization of the first polarizer and / or the second polarizer is 99% or more.   The liquid crystal panel according to claim 1, wherein the first polarizer and / or the second polarizer contains iodine. The difference (ΔI = I ₂ −I ₁ ) between the iodine content (I ₂ ) of the _second polarizer and the iodine content (I ₁ ) of the first polarizer is 0.1 to 2.6 weights. The liquid crystal panel according to claim 6, which is%. The iodine content of the first polarizer _{(I 1)} is 1.8 to 3.5 wt%, the liquid crystal panel according to claim 6 or 7. The liquid crystal panel according to claim 6, wherein an iodine content (I ₂ ) of the second polarizer is 2.3 to 5.0% by weight. A first retardation layer between the liquid crystal cell and the first polarizer, the first retardation layer including a first O plate;
10. The liquid crystal cell according to claim 1, further comprising a second retardation layer between the liquid crystal cell and the second polarizer, wherein the second retardation layer includes a second O plate. LCD panel.   The liquid crystal according to claim 10, wherein a direction in which an optical axis direction of each of the first O plate and the second O plate is projected onto the liquid crystal cell surface is substantially the same as an alignment processing direction of the liquid crystal cell. panel.   The angle formed by the slow axis of the first O plate and the absorption axis of the first polarizer is substantially 45 °, and the slow axis of the second O plate and the second polarizer The liquid crystal panel according to claim 10 or 11, wherein an angle formed by the absorption axis of the liquid crystal is substantially 45 °.   A liquid crystal display device comprising the liquid crystal panel according to claim 1.

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