JP2012145731A - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device showing excellent contrast in a frontal direction.SOLUTION: The liquid crystal panel includes a VA (vertical alignment) mode liquid crystal cell, a first polarizing plate disposed on one face of the liquid crystal cell, and a second polarizing plate disposed on the other face of the liquid crystal cell. The first polarizing plate comprises a first polarizer and a protective layer laminated on a face opposite to the liquid crystal cell side of the first polarizer. The second polarizing plate comprises a second polarizer, a protective layer laminated on a face opposite to the liquid crystal cell side of the second polarizer, and a retardation layer laminated on a face close to the liquid crystal cell side of the second polarizer. Each of the first polarizer and the second polarizer satisfies the relationship of 0.030≤R≤0.040 where Ris expressed by R=nx-ny with nx representing a refractive index within a plane of the polarizer in a direction where the refractive index reaches the maximum at a wavelength of 1000 nm, and ny representing a refractive index in a direction perpendicular to the direction where the refractive index reaches the maximum.

Description

  The present invention relates to a liquid crystal panel capable of providing a liquid crystal display device excellent in contrast characteristics in the front direction, and a liquid crystal display device using the liquid crystal panel.

  A liquid crystal display device (hereinafter referred to as LCD) is a device that displays characters and images using the electro-optical characteristics of liquid crystal molecules. The LCD normally uses a liquid crystal panel in which polarizing plates are arranged on both sides of the liquid crystal cell. For example, in the normally black method, a black image can be displayed in a state where no voltage is applied. The LCD has a problem that the contrast ratio in the front and oblique directions is low.

  As a method of improving the contrast of the liquid crystal display device, there is a method of improving the contrast of the polarizing plate, that is, the ratio of the single transmittance and the orthogonal transmittance of the polarizing plate. However, as the draw ratio is increased, drawing breakage or the like occurs, so that workability is deteriorated and productivity may be lowered.

  In addition, as the use of liquid crystal display devices expands, demands for thinning and low cost of liquid crystal display devices are increasing, and thinning and low cost of polarizing plates, which are essential components of liquid crystal display devices, are also increasing. Is desired. However, since PVA polarizers are poor in mechanical properties and optical durability, in a polarizing plate provided with a protective layer only on one side, the dimensional change of the polarizer and deterioration of the optical characteristics are likely to occur. Such a problem is remarkable in a humidified environment. Therefore, a polarizing plate provided with a protective layer on both sides of a polarizer is usually used (see, for example, Patent Document 1).

JP 2006-23573 A

  An object of the present invention is to provide a liquid crystal display device that realizes an improvement in contrast in the front direction, and a liquid crystal panel that can provide the liquid crystal display.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by a liquid crystal panel shown below, and have completed the present invention.

The liquid crystal panel of the present invention comprises a VA mode liquid crystal cell, a first polarizing plate disposed on one surface of the liquid crystal cell, and a second polarizing plate disposed on the other surface of the liquid crystal cell. The first polarizing plate includes a first polarizer and a protective layer laminated on a surface of the first polarizer opposite to the liquid crystal cell, and the second polarizing plate includes A second polarizer, a protective layer laminated on a surface of the second polarizer opposite to the liquid crystal cell, and a layer laminated on a surface of the second polarizer on the liquid crystal cell side. And R _pva of the first polarizer and the second polarizer satisfy a relationship of 0.030 ≦ R _pva ≦ 0.040, respectively. Here, R _pva is, when the wavelength is 1000 nm, the refractive index in the direction in which the refractive index is maximum in the plane of the polarizer is nx, and the refractive index in the direction orthogonal to the direction in which the refractive index is maximum is ny. , R _pva = nx−ny.
In a preferred embodiment, each of the first polarizer and the second polarizer is obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film.
In a preferred embodiment, the protective layer is a cellulose acetate resin film.
In a preferred embodiment, the protective layer of the first polarizing plate is a film subjected to an antiglare treatment.
In a preferred embodiment, the refractive index ellipsoid of the retardation layer has a relationship of nx>ny> nz, and the retardation Rth [590] in the thickness direction of the retardation layer is 150 nm to 400 nm.
In a preferred embodiment, the retardation layer is a cellulose acetate resin film or a cycloolefin resin film.
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.

The liquid crystal panel of the present invention improves the polarization characteristics without increasing the stretching ratio of the polarizer by setting R _pva of the polarizer contained in the polarizing plate to 0.030 ≦ R _pva ≦ 0.040, The contrast in the front direction can be improved.

It is a schematic sectional drawing of the liquid crystal panel in preferable embodiment of this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention.

<Definition of terms and symbols>
The definitions of terms and symbols in this specification are as follows.
(1) 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), and “ny” is the direction orthogonal to the slow axis in the plane (ie, the fast axis direction). “Nz” is the refractive index in the thickness direction.
(2) In-plane retardation value:
The in-plane retardation value (Re [λ]) refers to the in-plane retardation value of the film at a wavelength λ (nm) at 23 ° C. Re [λ] is obtained by Re [λ] = (nx−ny) × d, where d (nm) is the thickness of the film.
(3) Thickness direction retardation value:
The retardation value in the thickness direction (Rth [λ]) refers to the retardation value in the thickness direction of the film at 23 ° C. and the wavelength λ (nm). Rth [λ] is determined by Rth [λ] = (nx−nz) × d, where d (nm) is the thickness of the film.
(4) Nz coefficient:
The Nz coefficient is a value calculated by the formula: Rth [590] / Re [590].
(5) In this specification, the description “nx = ny” or “ny = nz” includes not only the case where they are completely the same, but also the case where they are substantially the same. Therefore, for example, the description of nx = ny includes the case where Re [590] is less than 10 nm.
(6) In this specification, “substantially orthogonal” includes a case where an angle formed by two optical axes is 90 ° ± 2 °, and preferably 90 ° ± 1 °. “Substantially parallel” includes a case where an angle formed by two optical axes is 0 ° ± 2 °, and preferably 0 ° ± 1 °.

<A. Overview of LCD panel>
FIG. 1 is a schematic cross-sectional view of a liquid crystal panel according to a preferred embodiment of the present invention. In the embodiment of FIG. 1, the liquid crystal panel 100 includes a first polarizing plate 10, a VA mode liquid crystal cell 20, and a second polarizing plate 30 in this order from the viewing side. The first polarizing plate 10 includes a first polarizer 11 and a protective layer 12 disposed on one surface of the first polarizer 11. The first polarizing plate 10 can be arranged so that the first polarizer 11 and the liquid crystal cell 20 face each other through an arbitrary adhesive layer (not shown). The second polarizing plate 30 is disposed on the second polarizer 31, the protective layer 32 disposed on one surface of the second polarizer 31, and the other surface of the second polarizer 31. And the retardation layer 33. The second polarizing plate 30 can be disposed such that the retardation layer 33 and the liquid crystal cell 20 face each other with an arbitrary adhesive layer (not shown) interposed therebetween. Preferably, the absorption axis of the first polarizer 11 included in the first polarizing plate 10 and the absorption axis of the second polarizer 31 included in the second polarizing plate 30 are arranged so as to be substantially orthogonal to each other. Can be done.

In the liquid crystal panel 100 of the present invention, the first polarizer 11 and the second polarizer 31 each satisfy the relationship that the value of R _pva is 0.030 ≦ R _pva ≦ 0.040. When the first polarizer 11 and the second polarizer 31 satisfy the above relationship, the contrast in the front direction can be improved.

  The retardation layer 33 is arranged so that its slow axis defines any appropriate angle with respect to the absorption axis of the second polarizer 31 according to the purpose, the configuration of the panel, and the like. For example, the slow axis of the retardation layer 33 and the absorption axis of the second polarizer 31 can be arranged to be substantially orthogonal.

<B. Liquid crystal cell>
Any appropriate liquid crystal cell may be employed as the liquid crystal cell used in the present invention. The liquid crystal cell preferably includes a pair of substrates and a liquid crystal layer as a display medium sandwiched between the pair of substrates. One substrate (active matrix substrate) includes a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the switching element, and a signal line for supplying a source signal. Provided. 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 (which may further include a multicolor light source) is used as the illumination means of the liquid crystal display device as in the field sequential method, the color filter can be omitted. The distance (cell gap) between the two substrates is controlled by a spacer. For example, an alignment film made of polyimide is provided on the side of each substrate in contact with the liquid crystal layer. Alternatively, for example, when the initial alignment of liquid crystal molecules is controlled using a fringe electric field formed by a patterned transparent electrode, the alignment film can be omitted.

  The liquid crystal cell preferably includes liquid crystal molecules aligned in a homeotropic alignment. In this specification, “homeotropic alignment” means a state in which the alignment vector of liquid crystal molecules is aligned perpendicularly (in the normal direction) to the substrate plane as a result of the interaction between the alignment-treated substrate and the liquid crystal molecules. Means things. The homeotropic alignment includes a case where the alignment vector of the liquid crystal molecules is slightly inclined with respect to the normal direction of the substrate, that is, the case where the liquid crystal molecules have a pretilt. When the liquid crystal molecules have a pretilt, the pretilt angle (angle from the substrate normal) is preferably 5 ° or less, more preferably 3 ° or less. By setting the pretilt angle in the above range, a liquid crystal display device with a high contrast ratio can be obtained.

  Any appropriate liquid crystal molecules can be adopted depending on the purpose. Preferably, the liquid crystal molecule is a nematic liquid crystal having a negative dielectric anisotropy. A nematic liquid crystal having a negative dielectric anisotropy is described in, for example, “Color Liquid Crystal Display” p. 196 The thing of FIG. 6.2.10 is mentioned. The birefringence of the nematic liquid crystal measured with light having a wavelength of 589 nm at 23 ° C. is preferably 0.05 to 0.15. The birefringence can be obtained from the difference (ne-no) by aligning liquid crystal molecules uniformly and uniformly, measuring the extraordinary refractive index (ne) and the ordinary refractive index (no).

  The driving mode of the liquid crystal cell is a vertical alignment (VA) mode. The VA mode liquid crystal cell utilizes a voltage-controlled birefringence effect, and makes liquid crystal molecules aligned in a homeotropic alignment respond to the substrate with an electric field in a normal direction in the absence of an electric field. Specifically, as described in, for example, Japanese Patent Application Laid-Open No. 62-210423 and Japanese Patent Application Laid-Open No. 4-153621, in the case of a normally black method, liquid crystal molecules are formed on a substrate in the absence of an electric field. Therefore, when the upper and lower polarizing plates are arranged orthogonally, a black display can be obtained. On the other hand, in the presence of an electric field, the liquid crystal molecules operate so as to tilt in a 45 ° azimuth direction with respect to the absorption axis of the polarizing plate, whereby the transmittance increases and white display is obtained.

  The VA mode liquid crystal cell can be multi-domained by using a substrate having slits formed on electrodes or a substrate having projections formed on the surface as described in JP-A-11-258605, for example. It may be what you did. Such a liquid crystal cell is, for example, an ASV (Advanced Super View) mode manufactured by Sharp Corporation, a CPA (Continuous Pinwheel Alignment) mode manufactured by the same company, an MVA (Multi-domain Vertical Alignment mode) manufactured by Fujitsu Limited, or the like. PVA (Patterned Vertical Alignment) mode manufactured by Co., Ltd., EVA (Enhanced Vertical Alignment) mode manufactured by the same company, SURVIVAL (Super Ranged Viewing by Vertical Alignment) mode manufactured by Sanyo Electric Co., Ltd., etc.

  As the liquid crystal cell, the one mounted on a commercially available liquid crystal display device may be used as it is. Commercially available liquid crystal display devices including VA mode liquid crystal cells include, for example, Sharp Corporation liquid crystal television product name “AQUIS series”, Sony liquid crystal television product name “BRAVIA series”, and SUMSUNG 32V type wide display. Liquid crystal television product name “LN32R51B”, Nanao Co., Ltd. liquid crystal television product name “FORIS SC26XD1”, AU Optronics liquid crystal television product name “T460HW01”, and the like.

<C. Polarizing plate>
The first polarizing plate 10 used in the present invention includes a first polarizer 11 and a protective layer 12. The second polarizing plate 30 used in the present invention includes a second polarizer 31, a protective layer 32 and a retardation layer 33.

The transmittance of the first polarizing plate and the second polarizing plate used in the present invention is preferably 38.3% to 44.3%, more preferably 39.2% to 44.2%, It is particularly preferably 41.1% to 44.2%, and most preferably 41.7% to 44.2%. When the transmittance is in such a range, a liquid crystal display device having a high contrast ratio in the front direction can be obtained. The transmittance is obtained as an average of the parallel transmittance T ₀ and the orthogonal transmittance T ₉₀ . Here, the parallel transmittance T ₀ is a transmittance value of a parallel laminated polarizer obtained by superimposing two identical polarizers so that their absorption axes are parallel to each other, and the orthogonal transmittance T ₉₀ is the same. This is a transmittance value of an orthogonal laminated polarizer obtained by superposing two polarizers so that their absorption axes are orthogonal to each other. Further, these transmittances are Y values obtained by correcting the visibility with the 2-degree field of view (C light source) of JlS Z 8701-1982. The transmittance can be measured using, for example, a spectrophotometer V7100.

  The degree of polarization of the first polarizing plate and the second polarizing plate used in the present invention is preferably 99% or more, more preferably 99.5% or more, and particularly preferably 99.7% or more. Most preferably, it is 99.8% or more. When the degree of polarization is in such a range, a liquid crystal display device having a high contrast ratio in the front direction can be obtained.

As a specific method for measuring the degree of polarization, the parallel transmittance (T ₀ ) and orthogonal transmittance (T ₉₀ ) of the polarizing plate are measured, and the formula: degree of polarization (%) = {(T ₀ -T ₉₀ ) / (T ₀ + T ₉₀ )} ^1/2 × 100. The parallel transmittance T ₀ and the orthogonal transmittance T ₉₀ are the same as in the case of the above transmittance. The degree of polarization can be measured using a spectrophotometer V7100.

<C-1. Polarizer>
Each of the first polarizer and the second polarizer used in the present invention satisfies 0.030 ≦ R _pva ≦ 0.040. Here, R _pva is, when the wavelength is 1000 nm, the refractive index in the direction in which the refractive index is maximum in the plane of the polarizer is nx, and the refractive index in the direction orthogonal to the direction in which the refractive index is maximum is ny. , R _pva = nx−ny. The first polarizer and the second polarizer may have R _pva in the above range, and may be the same polarizer or different polarizers. R _pva is preferably 0.030 ≦ R _pva ≦ 0.039, more preferably 0.030 ≦ R _pva ≦ 0.035. By satisfying these characteristics, the polarizer used in the present invention can have excellent dimensional stability and optical durability in a humidified environment. As a result, even when the polarizer used in the present invention is used in a polarizing plate provided with a protective layer only on one side of the polarizer, dimensional change and optical property deterioration are unlikely to occur, and practically acceptable dimensional stability. And optical durability can be realized. Therefore, the liquid crystal panel used in the present invention can be thinned without reducing productivity, and can provide a liquid crystal display device with improved front contrast.

  The polarizer used in the present invention is preferably composed mainly of a polyvinyl alcohol (PVA) resin containing a dichroic substance such as iodine or a dichroic dye.

  The iodine content of the polarizer used in the present invention is preferably 1.8% by weight to 5.0% by weight, and more preferably 2.0% by weight to 4.0% by weight. By setting the iodine content in the above range, a polarizing plate having a transmittance in a preferable range can be obtained, and a liquid crystal display device having a high contrast ratio in the front direction can be obtained.

  The boric acid content of the polarizer used in the present invention is preferably 0.5% to 3.0% by weight, more preferably 1.0% to 2.8% by weight, in terms of boron. Particularly preferably, it is 1.5% by weight to 2.6% by weight. As described above, according to the present invention, a polarizer having excellent dimensional stability and optical durability in a humidified environment can be obtained without increasing the amount of boric acid.

  The polarizer used in the present invention may preferably further contain potassium. The potassium content is preferably 0.2% by weight to 1.0% by weight, more preferably 0.3% by weight to 0.9% by weight, and particularly preferably 0.4% by weight to 0.00%. 8% by weight. By making potassium content into the said range, the polarizing plate which has the transmittance | permeability of a preferable range and has high polarization degree can be obtained.

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

  As the average degree of polymerization of the PVA-based resin, an appropriate value can be selected 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.

  The thickness of the polarizer used in the present invention is not particularly limited, and an appropriate thickness can be adopted depending on the purpose. The thickness is typically about 1 μm to 80 μm.

<C-2. Protective layer>
The protective layers 12 and 32 are formed of any appropriate film that can be used as a protective layer for a polarizing plate. Specific examples of the material as the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based materials. And transparent resins such as polystyrene, polynorbornene, polyolefin, (meth) acryl, and acetate. Preferably, the protective layers 12 and 32 include a cellulose acetate film. Further, thermosetting resins such as (meth) acrylic, urethane-based, (meth) acrylurethane-based, epoxy-based, and silicone-based or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in the side chain For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition.

The protective layer preferably has a linear expansion coefficient α in a direction parallel to the transmission axis of the polarizer of the protective layer smaller than the linear expansion coefficient in the transmission axis direction of the polarizer. By using such a protective layer, the crack durability can be improved. In one embodiment, the linear expansion coefficient α of the protective layer is preferably 4.5 × 10 ⁻⁵ / ° C. or less, and is −5.0 × 10 ⁻⁵ / ° C. to 4.5 × 10 ^−5. more preferably from / ° C., more preferably from ^{-4.5 × 10 -5 /℃~4.0×10 -5 / ℃} .

  As the protective layer of the polarizing plate, it is sufficient that at least one of the linear expansion coefficient in the TD direction and the linear expansion coefficient in the MD direction is smaller than the linear expansion coefficient in the transmission axis direction of the polarizer. Formed with any suitable film that can be used. What is necessary is just to arrange | position such a film so that the linear expansion coefficient of the direction parallel to the transmission axis of a polarizer may become smaller than the linear expansion coefficient of the transmission axis direction of a polarizer. The specific example of the material used as the main component of the film is as described above. Preferably, the film is a film mainly composed of a cellulose resin, a polyester resin or a polyimide resin, more preferably a triacetyl cellulose resin, a polyethylene terephthalate resin, a polyethylene naphthalate resin or a polyimide resin as a main component. It is a film. Preferably, the protective layer is a stretched film.

  The protective layer may be a transparent resin layer containing particles. The transparent resin layer containing the particles includes a transparent binder resin and particles. Any appropriate resin can be used as the transparent binder resin. Specifically, the resin exemplified as the main component of the film used as the protective layer may be used. Any appropriate particles can be used as the particles, and the particles may be inorganic particles or resin particles. The average particle diameter of the particles is preferably 0.05 μm to 2.0 μm.

  The protective layers (outer protective layers) 12 and 32 may be subjected to any appropriate surface treatment on the surfaces thereof. 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 an antiglare treatment, a diffusion treatment (antiglare treatment), an antireflection treatment (antireflection treatment), a hard coat treatment, and an antistatic treatment. The protective layer 12 on the viewing side is preferably subjected to an antiglare treatment. Since the antiglare treatment is performed on the protective layer 12 disposed on the viewing side, the contrast in the front direction can be further improved. Any appropriate method can be used as the anti-glare treatment method. For example, the surface reflection light can be formed by an appropriate method such as embossing, sand blasting, etching, or the like by providing a fine uneven structure on the surface.

<C-3. Retardation layer>
The retardation layer 33 used in the present invention is disposed on one surface of the second polarizer 31. In the retardation layer 33, the refractive index ellipsoid preferably has a relationship of nx>ny> nz, and the retardation Rth [590] in the thickness direction of the retardation layer 33 is 150 nm to 400 nm. By using the above retardation film, there is an advantage that a liquid crystal panel can be optically compensated only by arranging one retardation layer, and a thin and low-cost liquid crystal panel can be obtained.

  Re [590] of the retardation layer is preferably 10 nm or more, more preferably 20 nm to 80 nm, still more preferably 30 nm to 70 nm, and particularly preferably 40 nm to 70 nm. By setting Re [590] in the above range, a liquid crystal display device having a high contrast ratio in the front direction and excellent display characteristics can be obtained.

  The retardation Rth [590] in the thickness direction of the retardation layer is preferably 150 nm to 400 nm, more preferably 180 nm to 300 nm, and more preferably 200 nm to 300 nm. By setting Rth [590] in the above range, a liquid crystal display device having a high contrast ratio in the front direction and excellent display characteristics can be obtained.

  When the refractive index ellipsoid of the retardation layer shows a relationship of nx> ny> nz, Rth [590] is larger than Re [590]. That is, the Nz coefficient of the retardation layer is greater than 1. The Nz coefficient is preferably more than 1.1 and 8 or less, more preferably 2 to 7, and particularly preferably 2 to 6. By setting the Nz coefficient in the above range, a liquid crystal display device having a high contrast ratio in the front direction and excellent display characteristics can be obtained.

  The thickness of the retardation layer is preferably 0.5 μm to 200 μm.

  As a material for forming the retardation layer, any appropriate material can be used as long as the retardation layer has the above-described characteristics. The retardation layer is preferably a retardation film containing a cycloolefin resin such as a cellulose resin or a norbornene resin.

[Cellulosic resin]
Arbitrary appropriate things can be employ | adopted for the said cellulose resin. The cellulose resin is preferably a cellulose organic acid ester or a cellulose mixed organic acid ester in which some or all of the hydroxyl groups of cellulose are substituted with acetyl groups, propionyl groups, and / or butyl groups. Examples of the cellulose organic acid ester include cellulose acetate, cellulose propionate, and cellulose butyrate. Examples of the cellulose mixed organic acid ester include cellulose acetate propionate and cellulose acetate butyrate. The cellulose resin can be obtained by, for example, the method described in JP 2001-188128 A [0040] to [0041].

  The acetyl substitution degree of the cellulose acetate is preferably 2.0 to 3.0, more preferably 2.5 to 3.0. The propionyl substitution degree of the cellulose propionate is preferably 2.0 to 3.0, more preferably 2.5 to 3.0. When the cellulose-based resin is a mixed organic acid ester in which a part of the hydroxyl groups of cellulose is substituted with an acetyl group and a part thereof is substituted with a propionyl group, the total of the degree of acetyl substitution and the degree of propionyl substitution is preferably 2 It is 0.0-3.0, More preferably, it is 2.5-3.0. In this case, the degree of acetyl substitution is preferably 0.1 to 2.9, and the degree of propionyl substitution is preferably 0.1 to 2.9.

  In the present specification, the acetyl substitution degree (or propionyl substitution degree) indicates the number of hydroxyl groups attached to carbons at the 2, 3, 6 positions in the cellulose skeleton with acetyl groups (or propionyl groups). The acetyl group (or propionyl group) may be biased to any of the carbons at the 2, 3 and 6 positions of the cellulose skeleton, and may be present on average in each carbon. The said acetyl substitution degree can be calculated | required by ASTM-D817-91 (test methods, such as a cellulose acetate). Moreover, the said propionyl substitution degree can be calculated | required by ASTM-D817-96 (test methods, such as a cellulose acetate).

  The weight average molecular weight (Mw) of the cellulose resin is preferably 20,000 to 1,000,000, as measured by gel permeation chromatography (polystyrene standard) using a tetrahydrofuran solvent. The glass transition temperature (Tg) of the cellulose resin is preferably 110 ° C to 185 ° C. The glass transition temperature (Tg) can be determined by a DSC method according to JIS K7121. If it is said resin, it has the outstanding thermal stability and the film excellent in mechanical strength can be obtained.

  The retardation film containing the cellulose resin can be obtained by any appropriate forming method. Preferably, the retardation film containing the cellulose-based resin is a film formed into a sheet shape by a solvent casting method, a horizontal uniaxial stretching method, a vertical and horizontal simultaneous biaxial stretching method, or a vertical and horizontal sequential biaxial stretching method. Made by stretching. The temperature at which the film is stretched (stretching temperature) is preferably 120 ° C to 200 ° C. Moreover, the magnification (stretching ratio) for stretching the film is preferably more than 1 and not more than 3 times.

  As the retardation film, a commercially available film can be used as it is. Alternatively, a commercially available film subjected to secondary processing such as stretching and / or shrinking can be used. As a polymer film containing a commercially available cellulose resin, for example, Fuji Photo Film Co., Ltd. Fujitac series (trade name: ZRF80S, TD80UF, TDY-80UL), Konica Minolta Opto Co., Ltd. trade name “KC8UX2M” Or the like.

[Cycloolefin resin]
For example, a norbornene resin can be suitably used as the cycloolefin resin. Since the norbornene-based resin has a small absolute value (C [590]) of the photoelastic coefficient, a liquid crystal display device with small optical unevenness can be obtained. C [590] of the norbornene-based resin is preferably 1 × 10 ^{−12 to} 20 × 10 ⁻¹² , and more preferably 1 × 10 ⁻¹² to 10 × 10 ⁻¹² . In this specification, the “norbornene-based resin” refers to a (co) polymer obtained by using a norbornene-based monomer having a norbornene ring as a part or all of a starting material (monomer). The “(co) polymer” represents a homopolymer or a copolymer (copolymer).

In the norbornene-based resin, a norbornene-based monomer having a norbornene ring (having a double bond in the norbornane ring) is used as a starting material. In the state of the (co) polymer, the norbornene-based resin may or may not have a norbornane ring in the structural unit. In the state of the (co) polymer, the norbornene-based resin having a norbornane ring as a structural unit is, for example, tetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] Dec-3-ene, 8-methyltetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] dec-3-ene, 8-methoxycarbonyltetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] Dec-3-ene and the like. A norbornene-based resin having no norbornane ring as a structural unit in the (co) polymer state is, for example, a (co) polymer obtained using a monomer that becomes a 5-membered ring by cleavage. Examples of the monomer that becomes a 5-membered ring by cleavage include norbornene, dicyclopentadiene, 5-phenylnorbornene, and derivatives thereof. When the norbornene-based resin is a copolymer, the arrangement state of the molecules is not particularly limited, and may be a random copolymer, a block copolymer, or a graft copolymer. It may be.

  Examples of the norbornene resin include (A) a resin obtained by hydrogenating a ring-opening (co) polymer of a norbornene monomer, and (B) a resin obtained by addition (co) polymerization of a norbornene monomer. The ring-opening copolymer of the norbornene-based monomer is a resin obtained by hydrogenating a ring-opening copolymer of one or more norbornene-based monomers and α-olefins, cycloalkenes, and / or non-conjugated dienes. Include. The resin obtained by addition copolymerization of the norbornene monomer includes a resin obtained by addition copolymerization of one or more norbornene monomers with α-olefins, cycloalkenes and / or non-conjugated dienes.

  A resin obtained by hydrogenating the ring-opening (co) polymer of the norbornene monomer is subjected to a metathesis reaction of the norbornene monomer or the like to obtain a ring-opening (co) polymer. It can be obtained by hydrogenation. Specifically, for example, the method described in paragraphs [0059] to [0060] of JP-A-11-116780, the method described in paragraphs [0035] to [0037] of JP-A-2001-350017, and the like. Can be mentioned. The resin obtained by addition (co) polymerization of the norbornene monomer can be obtained, for example, by the method described in Example 1 of JP-A No. 61-292601.

  The weight average molecular weight (Mw) of the norbornene resin is preferably 20,000 to 500,000 as measured by gel permeation chromatography (polystyrene standard) using a tetrahydrofuran solvent. The glass transition temperature (Tg) of the norbornene-based resin is preferably 120 ° C to 170 ° C. If it is said resin, it has the outstanding thermal stability and the film excellent in the drawability can be obtained. The glass transition temperature (Tg) is a value calculated by the DSC method according to JIS K7121.

  The retardation film containing the norbornene resin can be obtained by any appropriate forming method. Preferably, the retardation film containing the norbornene-based resin is obtained by converting a polymer film formed into a sheet shape by a solvent casting method or a melt extrusion method into a transverse uniaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, or a longitudinal and transverse sequential two-phase method. It is produced by stretching by an axial stretching method. The temperature at which the polymer film is stretched (stretching temperature) is preferably 120 ° C to 200 ° C. Moreover, the magnification (stretching ratio) for stretching the polymer film is preferably more than 1 and not more than 3 times.

  The retardation film may further contain any appropriate additive. Examples of the additive include a plasticizer, a heat stabilizer, a light stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, a flame retardant, a colorant, an antistatic agent, a compatibilizer, a crosslinking agent, and a thickener. Etc. The content of the additive is preferably more than 0 and 10 parts by weight or less with respect to 100 parts by weight of the norbornene resin.

  The first polarizer 11 and the protective layer 12 in the first polarizing plate 10, the second polarizer 31 and the protective layer 32 in the second polarizing plate 30, the second polarizer 31 and the retardation layer 33, Can be laminated via any suitable adhesive layer. In this specification, the “adhesive layer” refers to a layer that joins surfaces of adjacent optical members and integrates them with practically sufficient adhesive force and adhesion time. Examples of the material for forming the adhesive layer include an adhesive, a pressure-sensitive adhesive, and an anchor coating agent. The adhesive layer may have a multilayer structure in which an anchor coat layer is formed on the surface of an adherend and an adhesive layer is formed thereon. Further, it may be a thin layer (also referred to as a hairline) that cannot be visually recognized.

  The thickness of the adhesive layer can be set to any appropriate value depending on the purpose. The thickness of the adhesive layer is preferably 0.01 μm to 50 μm. By setting the thickness of the adhesive layer in the above range, the polarizer to be joined does not float or peel off, and a practically sufficient adhesive force and adhesive time can be obtained.

  Any appropriate material can be selected as the material for forming the adhesive layer depending on the type and purpose of the adherend. In the case where the polarizer contains a polyvinyl alcohol resin containing iodine as a main component, the material for forming the adhesive layer is preferably a water-soluble adhesive. The water-soluble adhesive is preferably a water-soluble adhesive mainly composed of a polyvinyl alcohol resin. A commercially available adhesive can be used as it is for the adhesive layer. Or a solvent and an additive can also be mixed and used for a commercially available adhesive agent. As an adhesive mainly composed of a commercially available polyvinyl alcohol resin, for example, GOHSENOL series (trade name “NH-18S, GH-18S, T-300, etc.”) manufactured by Nippon Synthetic Chemical Industry Co., Ltd., the company Manufactured by Gohse-Fimer series (trade names “Z-100, Z-200, Z-210, etc.”) and the like.

<D. Adhesive layer>
In preferable embodiment, the said polarizing plate (a 1st polarizing plate and a 2nd polarizing plate) is affixed on the other member which comprises a liquid crystal panel through an contact bonding layer. As the material for forming the adhesive layer, an appropriate adhesive and / or anchor coat agent can be selected according to the type and application of the adherend. Specific examples of adhesives include solvent-based adhesives, emulsion-type adhesives, pressure-sensitive adhesives, rehumidifying adhesives, polycondensation-type adhesives, solventless adhesives, and film-like adhesives according to the classification by shape. Agents, hot melt adhesives, and the like. According to the classification by chemical structure, synthetic resin adhesives, rubber adhesives, and natural product adhesives can be mentioned. The adhesive includes a viscoelastic substance (also referred to as an adhesive) that exhibits an adhesive force that can be sensed by pressure contact at room temperature.

  Preferably, the material forming the adhesive layer is a pressure-sensitive adhesive (also referred to as an acrylic pressure-sensitive adhesive) having an acrylic polymer as a base polymer. It is because it is excellent in transparency, adhesiveness, weather resistance, and heat resistance. The thickness of the acrylic pressure-sensitive adhesive layer can be appropriately adjusted according to the material and application of the adherend, but is usually 5 μm to 50 μm.

<E. Manufacturing method of liquid crystal panel>
The liquid crystal panel used in the present invention can be produced, for example, by sequentially laminating the above constituent elements (first and second polarizers, protective layer, retardation layer) on a liquid crystal cell. For example, the 1st laminated body (1st polarizing plate) by which the 1st polarizer and the protective layer were laminated | stacked, and the 2nd by which the 2nd polarizer, phase difference layer, and the protective layer were laminated | stacked. The laminate (second polarizing plate) may be prepared, and then the first and second laminates may be bonded to a liquid crystal cell.

  A polarizer using a conventional PVA-based resin is inferior in dimensional stability. Therefore, in a polarizing plate in which a protective layer is provided only on one side, the dimensional change of the polarizer is likely to occur. For example, curling occurs in the polarizing plate. Therefore, lamination with other members such as a liquid crystal cell becomes difficult, resulting in poor productivity. However, since the first polarizer and the second polarizer used in the liquid crystal panel used in the present invention are excellent in dimensional stability particularly in a humidified environment, the first polarizing plate and the second polarizing plate. As described above, even when the protective layer is laminated only on one side, the occurrence of curling due to the dimensional change of the polarizer can be suppressed. Thereby, it becomes possible to laminate | stack the polarizing plate which has a protective layer only on the one side which was difficult conventionally, and productivity improves. Further, by reducing the number of protective layers included in the liquid crystal panel, the influence on the display characteristics due to the optical characteristics of the protective layers can be suppressed, and the liquid crystal display device can be reduced in thickness.

  Any appropriate method can be adopted as a method of laminating each component of the liquid crystal panel. Typically, it is laminated via any suitable adhesive layer (not shown). As a material for forming the adhesive layer, the materials described in the above section D can be used.

<F. Liquid crystal display>
The liquid crystal display device of the present invention includes the liquid crystal panel. FIG. 2 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. It should be noted that the ratios of the vertical, horizontal, and thickness of each component shown in FIG. 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 100. In the illustrated example, the case where the direct type is adopted as the backlight unit is shown, but this may be a side light type, for example.

  When the direct type is adopted, the backlight unit 80 preferably includes a light source 81, a reflection film 82, a diffusion plate 83, a prism sheet 84, and a brightness enhancement film 85. When the sidelight system is adopted, preferably, the backlight unit further includes a light guide plate and a light reflector in addition to the above configuration. In addition, as long as the optical member illustrated in FIG. 2 has the effect of the present invention, a part of the optical member such as an illumination method of a liquid crystal display device or a driving mode of a liquid crystal cell can be omitted or other The optical member can be replaced.

  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.

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) R _pva
About the polarizer used by the Example and the comparative example, it measured using the near infrared phase difference measuring apparatus KOBRA-31X100 / IR (wavelength 1000nm, 23 degreeC) by the Oji Scientific Instruments company.
(2) Panel contrast The liquid crystal panel obtained in each example or comparative example was manufactured using a liquid crystal television (manufactured by Sharp Corporation) so that the first polarizing plate was on the viewing side and the second polarizing plate was on the backlight side. In the backlight unit of “LC-32DE5”). About the obtained liquid crystal display device, contrast was computed in SR-UL1R made from Topcon.

[Reference Example 1]
A PVA resin film having a polymerization degree of 2400, a saponification degree of 99.7 mol%, and a thickness of 75 μm was prepared. The film was stretched 3 times in the film transport direction while being dyed in an aqueous iodine solution at 30 ° C., and then the total draw ratio was 4% by weight boric acid at 60 ° C. and 5% by weight potassium iodide aqueous solution. The film was stretched to be 6 times the original length. Furthermore, the stretched film was washed by immersing it in a 2 wt% potassium iodide aqueous solution at 30 ° C. for several seconds. The obtained stretched film was dried at 90 ° C. to obtain a polarizer (1). R _pva of the obtained polarizer (1) was 0.035.

[Reference Example 2]
A polarizer (2) was obtained in the same manner as in Reference Example 1 except that drying was performed at 80 ° C. R _pva of the obtained polarizer (2) was 0.038.

[Reference Example 3]
A polarizer (3) was obtained in the same manner as in Reference Example 1 except that drying was performed at 70 ° C. R _pva of the obtained polarizer (3) was 0.039.

[Reference Example 4]
A polarizer (4) was obtained in the same manner as in Reference Example 1 except that drying was performed at 60 ° C. and the total draw ratio was 4.8 times the original length. R _pva of the obtained polarizer (4) was 0.042.

[Reference Example 5]
A polarizer (5) was obtained in the same manner as in Reference Example 1 except that drying was performed at 50 ° C. and the total draw ratio was 5.3 times the original length. R _pva of the obtained polarizer (5) was 0.043.

[Reference Example 6]
A polarizer (6) was obtained in the same manner as in Reference Example 1 except that drying was performed at 40 ° C. and the total draw ratio was 6.2 times the original length. R _pva of the obtained polarizer (6) was 0.046.

[Example 1]
A protective layer was laminated on one surface of the polarizer (1) obtained in Reference Example 1 using a PVA adhesive and dried at 40 ° C. for 2 minutes. Next, an adhesive was laminated on the other surface of the polarizer (1) to obtain a first polarizing plate.
Similarly, a protective layer is provided on one surface of another polarizer (1), and a retardation layer is formed on the other surface (a refractive index ellipsoid has a relationship of nx>ny> nz, and Rth is 265 nm cellulose acetate film) ) Were laminated using a PVA adhesive and dried at 40 ° C. for 2 minutes. Then, a pressure-sensitive adhesive was laminated on the retardation layer laminated on the polarizer to obtain a second polarizing plate.
The polarizing plates on both sides were peeled from the liquid crystal cell of a commercially available liquid crystal television (“LC-32DE5” manufactured by Sharp Corporation) equipped with a VA mode liquid crystal display element. A first polarizing plate was attached to one side of the liquid crystal cell so that the first polarizer and the liquid crystal cell were opposed to each other. Next, a second polarizing plate was attached to the other side of the liquid crystal cell so that the retardation layer and the liquid crystal cell face each other. At this time, the second polarizing plate is attached so that the absorption axis of the second polarizing plate is orthogonal to the horizontal direction of the liquid crystal cell and the absorption axis of the first polarizing plate is parallel to the horizontal direction of the liquid crystal cell. Panel 1 was produced. Table 1 shows the contrast of the liquid crystal display device using the obtained liquid crystal panel and the R _{pva of} the polarizer used in the liquid crystal panel.

[Example 2]
A liquid crystal panel 2 was produced in the same manner as in Example 1 except that the polarizer (2) obtained in Reference Example 2 was used. Table 1 shows the contrast of the liquid crystal display device using the obtained liquid crystal panel and the R _{pva of} the polarizer used in the liquid crystal panel.

[Example 3]
A liquid crystal panel 3 was produced in the same manner as in Example 1 except that the polarizer (3) obtained in Reference Example 3 was used. Table 1 shows the contrast of the liquid crystal display device using the obtained liquid crystal panel and the R _{pva of} the polarizer used in the liquid crystal panel.

[Comparative Example 1]
A liquid crystal panel 4 was obtained in the same manner as in Example 1 except that the polarizer (4) obtained in Reference Example 4 was used. Table 1 shows the contrast of the liquid crystal display device using the obtained liquid crystal panel and the R _{pva of} the polarizer used in the liquid crystal panel.

[Comparative Example 2]
A liquid crystal panel 5 was produced in the same manner as in Example 1 except that the polarizer (5) obtained in Reference Example 5 was used. Table 1 shows the contrast of the liquid crystal display device using the obtained liquid crystal panel and the R _{pva of} the polarizer used in the liquid crystal panel.

[Comparative Example 3]
A liquid crystal panel 6 was obtained in the same manner as in Example 1 except that the polarizer (6) obtained in Reference Example 6 was used. Table 1 shows the contrast of the liquid crystal display device using the obtained liquid crystal panel and the R _{pva of} the polarizer used in the liquid crystal panel.

[Evaluation]
The liquid crystal display devices of Examples 1 to 3 of the present invention using the polarizer having R _pva of 0.040 or less are the liquid crystal display devices of Comparative Examples 1 to 3 using polarized light having R _pva of more than 0.040. Compared with that, it showed high contrast.

  As described above, since the liquid crystal panel of the present invention exhibits a high front contrast ratio when used in a liquid crystal display device, it is extremely useful for improving display characteristics of, for example, a liquid crystal television, a personal computer monitor, and a mobile phone. is there.

10 first polarizing plate 11 first polarizer 12 protective layer 20 liquid crystal cell 30 second polarizing plate 31 second polarizer 32 protective layer 33 retardation layer 80 backlight unit 81 light source 82 reflective film 83 diffuser plate 84 Prism sheet 85 Brightness enhancement film 100 LCD panel

Claims (7)

A VA mode liquid crystal cell;
A first polarizing plate disposed on one surface of the liquid crystal cell;
A second polarizing plate disposed on the other surface of the liquid crystal cell,
The first polarizing plate includes a first polarizer and a protective layer laminated on a surface of the first polarizer opposite to the liquid crystal cell,
The second polarizing plate includes a second polarizer, a protective layer laminated on a surface of the second polarizer opposite to the liquid crystal cell, and the liquid crystal cell side of the second polarizer. A retardation layer laminated on the surface of
First polarizer and the second polarizer _{R pva} satisfies the relationship 0.030 ≦ _{R pva} ≦ 0.040, respectively, the liquid crystal panel:
Here, R _pva is, when the wavelength is 1000 nm, the refractive index in the direction in which the refractive index is maximum in the plane of the polarizer is nx, and the refractive index in the direction orthogonal to the direction in which the refractive index is maximum is ny. , R _pva = nx−ny.   The liquid crystal panel according to claim 1, wherein each of the first polarizer and the second polarizer is obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film.   The liquid crystal panel according to claim 1, wherein the protective layer is a cellulose acetate resin film.   The liquid crystal panel according to any one of claims 1 to 3, wherein the protective layer of the first polarizing plate is a film subjected to an antiglare treatment. The refractive index ellipsoid of the retardation layer has a relationship of nx>ny> nz, and
The liquid crystal panel according to any one of claims 1 to 4, wherein a retardation Rth [590] in a thickness direction of the retardation layer is 150 nm to 400 nm.   The liquid crystal panel according to claim 1, wherein the retardation layer is a cellulose acetate resin film or a cycloolefin resin film.   A liquid crystal display device comprising the liquid crystal panel according to claim 1.

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