JP2006208925A - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

An object of the present invention is to provide a liquid crystal panel and a liquid crystal display device having a high contrast ratio in the oblique direction and a small amount of color shift in the oblique direction. In addition, a liquid crystal panel and a liquid crystal display device having good display uniformity are provided.
A liquid crystal cell, a polarizer disposed on both sides of the liquid crystal cell, a first optical element disposed between one of the polarizers and the liquid crystal cell, and the polarizer A second optical element disposed between the other of the liquid crystal cell and the liquid crystal cell, wherein the first optical element has a refractive index distribution of nx>nz> ny and a retardation value of λ / 2. And a stretched polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer, wherein the second optical element is substantially optically negative. LCD panel with uniaxiality.
[Selection] Figure 2

Description

  The present invention relates to a liquid crystal panel having a liquid crystal cell, a polarizer, and an optical element. The present invention also relates to a liquid crystal television and a liquid crystal display device using the liquid crystal panel.

  Liquid crystal display devices are attracting attention for their features such as thinness, light weight, and low power consumption. Mobile devices such as mobile phones and watches; OA devices such as personal computer monitors and laptop computers; and home appliances such as video cameras and liquid crystal televisions. Widely popular. This is because technical innovations are overcoming the drawbacks of changing display characteristics depending on the angle at which the screen is viewed and not operating at high or very low temperatures. However, the properties required for each application have changed as the applications are varied. For example, in a conventional liquid crystal display device, it has been considered that the viewing angle characteristic should have a contrast ratio of white / black display of about 10 in an oblique direction. This definition is derived from the contrast ratio of black ink printed on white paper such as newspapers and magazines. However, in stationary large color television applications, several people see the screen at the same time, so a display that can be seen well from different viewing angles is required. That is, the contrast ratio of white / black display is required to be 20 or more, for example. In addition, when the display becomes large, the person who looks at the screen does not move, but when viewing the four corners of the screen, it is the same as viewing from different viewing angles. It is important that there is no unevenness and the display is uniform.

  Currently, as one of the driving modes that are widely used in television applications, there is a liquid crystal display device including a vertical alignment (VA) liquid crystal cell. A feature of this system is that a clear black display can be obtained by a liquid crystal cell including a liquid crystal layer including a nematic liquid crystal aligned in a homeotropic alignment in the absence of an electric field. However, a liquid crystal display device having a conventional VA liquid crystal cell has a contrast ratio that decreases in an oblique direction, and coloration of an image that changes with the viewing angle (also referred to as an oblique color shift) occurs. As described above, there is a problem that display characteristics deteriorate.

  In order to solve this problem, a λ / 2 plate showing a refractive index distribution of nx> nz> ny (however, the refractive indexes in the slow axis direction, fast axis direction and thickness direction of the film are nx, nz and ny) and a retardation film exhibiting a refractive index distribution of nx = ny> nz (also referred to as having an optically negative uniaxial) can improve display characteristics in an oblique direction. Is disclosed (Patent Document 1). However, the disclosed technique does not sufficiently improve the contrast ratio in the oblique direction and the color shift in the oblique direction, and further improvement in display characteristics is desired.

  Conventionally, the λ / 2 plate exhibiting the refractive index distribution of nx> nz> ny described above discloses a polymer film mainly composed of aromatic resin such as polycarbonate resin, polyarylate resin, and polyester resin. (Patent Document 2, Patent Document 3). However, since the polymer film mainly composed of the aromatic resin as described above has a large absolute value of the photoelastic coefficient, the retardation value is likely to change with respect to the stress. For this reason, the phase difference value may deviate from the design value due to the contraction stress of the polarizer when exposed to high temperatures in a state of being bonded between the liquid crystal cell and the polarizer. It is a problem that display uniformity is deteriorated due to unevenness in retardation value due to unevenness in stress caused by the above.

On the other hand, a polymer film containing an aliphatic resin as a main component has a small absolute value of the photoelastic coefficient. However, since a polymer film containing an aliphatic resin as a main component does not easily generate a retardation, an aromatic polymer film is used when a retardation film showing a refractive index distribution of nx>nz> ny is to be produced. A desired retardation value cannot be obtained even if the film is stretched at a high stretch ratio, as well as at a low stretch ratio as described above. Moreover, since it extended | stretched with high draw ratio, it has been a problem that a film will fracture | rupture. Therefore, in the prior art, a retardation film having a relationship of nx ≧ ny> nz with a polymer film mainly composed of an aliphatic resin having a small absolute value of the photoelastic coefficient has been obtained (Patent Document 4). ), A retardation film having a relationship of nx>nz> ny has not been obtained.
JP 2000-039610 A JP-A-4-305602 JP-A-5-157911 JP 2001-215332 A

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a liquid crystal panel and a liquid crystal display device having a high contrast ratio in the oblique direction and a small amount of color shift in the oblique direction. It is another object of the present invention to provide a liquid crystal panel and a liquid crystal display device having good display uniformity that do not cause a shift or unevenness of a retardation value due to contraction stress of a polarizer or heat of a backlight.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the following liquid crystal panel and liquid crystal display device, and have completed the present invention.

A liquid crystal panel of the present invention includes a liquid crystal cell including a liquid crystal layer including a nematic liquid crystal aligned in a homeotropic alignment in the absence of an electric field, a polarizer disposed on both sides of the liquid crystal cell, and the polarizer A first optical element disposed between one of the liquid crystal cells and the liquid crystal cell, and a second optical element disposed between the other of the polarizers and the liquid crystal cell,
The first optical element satisfies the following formulas (1) and (2), and is a stretched polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer. Including
The second optical element has substantially optically negative uniaxiality:
200 nm ≦ Re [590] ≦ 350 nm (1)
0 nm <Rth [590] <Re [590] (2)
However, Re [590] and Rth [590] are an in-plane retardation value and a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C., respectively.

  In a preferred embodiment, the slow axis of the first optical element is substantially parallel or orthogonal to the absorption axis of one of the polarizers.

In a preferred embodiment, the second optical element satisfies the following formulas (3) and (4):
0 nm ≦ Re [590] ≦ 10 nm (3)
100 nm ≦ Rth [590] ≦ 800 nm (4)
However, Re [590] and Rth [590] are an in-plane retardation value and a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C., respectively.

  As a preferred embodiment, the second optical element includes a retardation film in which the difference between the in-plane main refractive index (nx) and the refractive index (nz) in the thickness direction is 0.03 to 0.20. .

  In a preferred embodiment, the retardation film is a polymer film containing polyimide as a main component.

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

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

  The liquid crystal panel of the present invention increases the contrast ratio in the oblique direction of the liquid crystal display device by disposing a specific component (typically, a retardation film) in a specific positional relationship, and the color shift amount in the oblique direction. Can be reduced. In addition, the liquid crystal display device incorporating the liquid crystal panel of the present invention has a stretched polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer as the first optical element. Therefore, the absolute value of the photoelastic coefficient of the retardation film can be reduced, and even when the backlight is lit for a long time, a film having good display uniformity can be obtained. Conventionally, a retardation film having a small photoelastic coefficient and a relationship of nx> nz> ny has not been obtained. On the other hand, according to the present invention, a shrinkable film having a predetermined shrinkage rate is bonded to both sides of a polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer, and stretched. By doing so, a retardation film having a small photoelastic coefficient absolute value and a relationship of nx> nz> ny can be actually obtained.

  In addition, a stretched film of a polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene-based monomer has excellent wavelength dispersion characteristics, and therefore has a conventional aromatic resin as a main component. The amount of color shift in the oblique direction of the liquid crystal display device can be made even smaller than when a stretched polymer film is used. Furthermore, when a retardation film having a substantially optically negative uniaxial property is produced using a material having a large birefringence in the thickness direction as the second optical element, the smoothness of the retardation film is reduced. A liquid crystal panel (as a result, a liquid crystal display device) can be obtained which is remarkably improved and extremely excellent in display uniformity. Conventionally, a retardation film used in a liquid crystal cell having a liquid crystal layer containing a nematic liquid crystal aligned in a homeotropic alignment is usually a retardation in the thickness direction of 200 nm or more in order to compensate for the retardation value of the liquid crystal cell. A value was required, and it was necessary to increase the thickness to about 100 μm. On the other hand, according to the present invention, for example, when a polymer film containing polyimide as a main component is used as the second optical element, the target retardation value in the thickness direction is obtained with one retardation film. In addition, the thickness of the retardation film can be significantly reduced to, for example, about 10 μm. By thinning the retardation film, a liquid crystal display device with extremely excellent display uniformity can be obtained.

A. Schematic diagram of the entire liquid crystal panel 1 is a schematic cross-sectional view of a liquid crystal panel according to a preferred embodiment of the present invention. FIG. 2 is a schematic perspective view of the liquid crystal panel. It should be noted that, for the sake of easy understanding, the ratio of the vertical, horizontal, and thickness of each component in FIGS. 1 and 2 is described differently from the actual one. The liquid crystal panel 100 includes a liquid crystal cell 10 including a liquid crystal layer including nematic liquid crystal aligned in a homeotropic alignment in the absence of an electric field, polarizers 21 and 22 disposed on both sides of the liquid crystal cell 10, and a polarizer. A first optical element 30 disposed between one of them (polarizer 21 in the illustrated example) and the liquid crystal cell 10, and the other of the polarizers (polarizer 22 in the illustrated example) and the liquid crystal cell 10. And a second optical element 40 disposed between the two. Practically, any appropriate protective layer (preferably an isotropic film / not shown) may be disposed outside the polarizers 21 and 22. In the illustrated example, the slow axis of the first optical element 30 and the absorption axis of the polarizer 21 are parallel to each other, but they may be orthogonal to each other. The first optical element 30 satisfies the following formulas (1) and (2), and is a stretched polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer. And the second optical element has a substantially optically negative uniaxiality:
200 nm ≦ Re [590] ≦ 350 nm (1)
0 nm <Rth [590] <Re [590] (2)
However, Re [590] and Rth [590] are an in-plane retardation value and a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C., respectively. Preferably, the polarizer 21 and the first optical element 30 are disposed on the viewing side of the liquid crystal cell 10, and the polarizer 22 and the second optical element 40 are disposed on the backlight side of the liquid crystal cell 10. By laminating such specific optical elements on the liquid crystal cell, extremely good optical compensation is performed. As a result, the contrast ratio in the oblique direction of the liquid crystal display device is high and the color shift amount in the oblique direction is small. A liquid crystal display device can be realized. In addition, the liquid crystal panel of the present invention is not limited to the above-described embodiment. For example, another constituent member (preferably an isotropic film) is disposed between the constituent members shown in FIG. There may be. Hereinafter, the constituent members of the liquid crystal panel of the present invention will be described in detail.

B. Liquid Crystal Cell Referring to FIG. 1, the liquid crystal cell 10 used in the liquid crystal panel of the present invention includes a pair of substrates 11 and 11 ′ and a liquid crystal layer 12 as a display medium sandwiched between the substrates 11 and 11 ′. Have One substrate (active matrix substrate) 11 ′ 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 active element, and a signal line for supplying a source signal. Are provided (both not shown). The other substrate (color filter substrate) 11 is provided with a color filter. The color filter may be provided on the active matrix substrate 11 ′. The distance (cell gap) between the substrates 11 and 11 ′ is controlled by a spacer (not shown). An alignment film (not shown) made of polyimide, for example, is provided on the side of the substrates 11 and 11 ′ in contact with the liquid crystal layer 12.

  The liquid crystal layer 12 includes nematic liquid crystal aligned in a homeotropic alignment in the absence of an electric field. Such a liquid crystal layer (as a result, a liquid crystal cell) typically exhibits a refractive index distribution of nz> nx = ny (where the in-plane refractive index is nx, ny, and the refractive index in the thickness direction is nz). In the present specification, nx = ny includes not only the case where nx and ny are completely the same, but also the case where nx and ny are substantially the same. A typical example of the drive mode using a liquid crystal layer exhibiting such a refractive index distribution is a vertical alignment (VA) mode. In a VA mode liquid crystal cell, a nematic with a negative dielectric anisotropy that is aligned in a homeotropic alignment in the absence of an electric field between transparent electrodes, utilizing the voltage controlled birefringence (ECB) effect. The liquid crystal is caused to respond with an electric field parallel to the substrate normal. More specifically, liquid crystal cells described in JP-A-62-210423 and JP-A-4-153621 are exemplified. Further, as described in JP-A No. 11-258605, the VA mode liquid crystal cell includes a substrate provided with a slit in a pixel or a projection formed on the surface in order to enlarge a viewing angle. May be used to form a multi-domain MVA mode liquid crystal cell. Further, as described in JP-A-10-123576, a VATN mode in which a chiral agent is added to liquid crystal, nematic liquid crystal is substantially vertically aligned when no voltage is applied, and twisted multi-domain alignment is applied when voltage is applied. The liquid crystal cell may be used.

  The nematic liquid crystal aligned in the homeotropic alignment means, for example, that the alignment vector of the nematic liquid crystal molecule is perpendicular to the substrate plane (in the normal direction) as a result of the interaction between the aligned substrate and the nematic liquid crystal molecule. ) And in a uniformly oriented state. In the present specification, even when the orientation vector is slightly inclined with respect to the normal direction of the substrate, that is, when the nematic liquid crystal molecule has a pretilt, it is included in the homeotropic alignment. When the nematic liquid crystal molecules have a pretilt, the pretilt angle is preferably 10 ° or less from the substrate normal from the viewpoint of maintaining a high contrast ratio and obtaining good display characteristics.

As the nematic liquid crystal, any appropriate nematic liquid crystal can be adopted depending on the purpose. For example, the nematic liquid crystal may have a positive or negative dielectric anisotropy. In the VA mode liquid crystal display device, nematic liquid crystal having negative dielectric anisotropy is preferably used. A specific example of a nematic liquid crystal having a positive dielectric anisotropy is a product name “ZLI-4535” manufactured by Merck & Co., Inc. A specific example of a nematic liquid crystal having a negative dielectric anisotropy is a product name “ZLI-2806” manufactured by Merck & Co., Inc. Further, 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 arbitrarily set according to the response speed, transmittance, etc. of the liquid crystal cell. Usually, it is preferably 0.05 to 0.30.

  Any appropriate cell gap may be adopted as the cell gap (substrate interval) of the liquid crystal cell depending on the purpose. The cell gap is preferably 1.0 μm to 7.0 μm. Within the above range, the response time can be shortened and good display characteristics can be obtained.

C. In the polarizer herein, a polarizer, refers to an optical film capable of converting natural light or polarized light into any polarized light. Any appropriate polarizer can be adopted as the polarizer used in the polarizing plate of the present invention. Preferably, a film that converts natural light or polarized light into linearly polarized light is used.

  Any appropriate thickness can be adopted as the thickness of the polarizer. The thickness of the polarizer is typically 5 μm to 80 μm, preferably 10 μm to 50 μm, and more preferably 20 μm to 40 μm. If it is said range, it is excellent in an optical characteristic and mechanical strength.

C-1. Optical Properties of Polarizer The transmittance of the above polarizer measured at 23 ° C. at a wavelength of 440 nm (also referred to as single transmittance) is preferably 41% or more, more preferably 43% or more. Note that the theoretical upper limit of the single transmittance is 50%. The degree of polarization is preferably 99.8% to 100%, and more preferably 99.9% to 100%. If it is said range, when it uses for a liquid crystal display device, the contrast ratio of a front direction can be made still higher.

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

C-2. Polarizer Arranging Means Referring to FIG. 2, any appropriate method can be adopted as a method of arranging the polarizer 21 and the polarizer 22 depending on the purpose. Preferably, the polarizers 21 and 22 are provided with an adhesive layer or an adhesive layer (not shown) on the surface facing the liquid crystal cell, and the polarizer 21 is polarized on the surface of the first optical element 30. The child 22 is bonded to the surface of the second optical element 40. By doing so, the contrast can be increased when used in a liquid crystal display device.

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

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

  Preferably, the polarizer 21 is arranged so that the absorption axis thereof is substantially perpendicular to the absorption axis of the opposing polarizer 22. In the present specification, “substantially orthogonal” includes a case where the angle formed by the absorption axis of the polarizer 21 and the absorption axis of the polarizer 22 is 90 ° ± 2.0 °, and preferably Is 90 ° ± 1.0 °, more preferably 90 ° ± 0.5 °. As the degree of deviation from these angular ranges increases, the contrast ratio in the front and oblique directions tends to decrease when used in a liquid crystal display device.

C-3. Optical Film Used for Polarizer The polarizer is made of, for example, a stretched polymer film mainly composed of a polyvinyl alcohol resin containing a dichroic substance. The polymer film containing the polyvinyl alcohol resin as a main component is produced, for example, by the method described in JP 2000-315144 A [Example 1].

  As said polyvinyl alcohol-type resin, what saponified the vinyl ester-type polymer obtained by superposing | polymerizing a vinyl ester-type monomer, and using the vinyl ester unit as a vinyl alcohol unit can be used. Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Of these, vinyl acetate is preferable.

  Any appropriate average degree of polymerization may be adopted as the average degree of polymerization of the polyvinyl alcohol resin. The average degree of polymerization is preferably 1200 to 3600, more preferably 1600 to 3200, and most preferably 1800 to 3000. The average degree of polymerization of the polyvinyl alcohol resin can be measured by a method according to JIS K 6726-1994.

  The saponification degree of the polyvinyl alcohol-based resin is preferably 90.0 to 99.9 mol%, more preferably 95.0 to 99.9 mol%, most preferably from the viewpoint of the durability of the polarizer. Is 98.0-99.9 mol%.

  The saponification degree indicates the proportion of units that are actually saponified to vinyl alcohol units among units that can be converted to vinyl alcohol units by saponification. The degree of saponification of the polyvinyl alcohol resin can be determined according to JIS K 6726-1994.

  The polymer film mainly composed of the polyvinyl alcohol-based resin used in the present invention can preferably contain a polyhydric alcohol as a plasticizer. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane. These may be used alone or in combination of two or more. In the present invention, ethylene glycol or glycerin is preferably used from the viewpoint of stretchability, transparency, thermal stability, and the like.

  The amount of polyhydric alcohol used in the present invention is preferably 1 to 30 (weight ratio), more preferably 3 to 25 (weight ratio), with respect to the total solid content 100 of the polyvinyl alcohol resin. Most preferably, it is 0.05-0.3 (weight ratio). If it is said range, dyeability and stretchability can be improved further.

  Any appropriate dichroic substance can be adopted as the dichroic substance. Specific examples include iodine or dichroic dyes. In this specification, “dichroism” refers to optical anisotropy in which light absorption is different in two directions, ie, an optical axis direction and a direction perpendicular thereto.

  Examples of the dichroic dye include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet. B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. are mentioned.

  An example of a method for manufacturing a polarizer will be described with reference to FIG. FIG. 3 is a schematic view showing the concept of a typical production process of a polarizer used in the present invention. For example, a polymer film 201 mainly composed of a polyvinyl alcohol-based resin is drawn out from the feeding portion 200, immersed in an iodine aqueous solution bath 210, and tension is applied in the film longitudinal direction by rolls 211 and 212 having different speed ratios. While being subjected to swelling and dyeing processes. Next, it is immersed in a bath 220 of an aqueous solution containing boric acid and potassium iodide, and subjected to a crosslinking treatment while tension is applied in the longitudinal direction of the film by rolls 221 and 222 having different speed ratios. The film subjected to the crosslinking treatment is immersed in an aqueous solution bath 230 containing potassium iodide by rolls 231 and 232 and subjected to a water washing treatment. The water-washed film is dried by the drying means 240 so that the moisture content is adjusted and wound by the winding unit 260. The polarizer 250 can be obtained by stretching the polymer film containing the polyvinyl alcohol resin as a main component 5 to 7 times the original length through these steps.

  Any appropriate moisture content can be adopted as the moisture content of the polarizer. Preferably, the moisture content is 5-40%, more preferably 10-30%, and most preferably 20-30%.

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

  In the liquid crystal panel of the present invention, the polarizers disposed on both sides of the liquid crystal cell may be the same or different.

D. First Optical Element Referring to FIGS. 1 and 2, the first optical element 30 is disposed between the liquid crystal cell 10 and the polarizer 21. According to such a configuration, the first optical element 30 functions as a protective layer on the liquid crystal cell side of the polarizer 21 to prevent the polarizer from being deteriorated. As a result, the display characteristics of the liquid crystal display device are improved. It can be kept high for a long time. The first optical element 30 satisfies the following formulas (1) and (2), and is a stretched polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer. Including.
200 nm ≦ Re [590] ≦ 350 nm (1)
0 nm <Rth [590] <Re [590] (2)
However, Re [590] and Rth [590] are a retardation value in the film plane and a retardation value in the thickness direction, respectively, measured with light having a wavelength of 590 nm at 23 ° C.

  In the present invention, the first optical element is used as a λ / 2 plate having an in-plane retardation value of about ½ with respect to the wavelength of light (usually in the visible light region). In this specification, “λ / 2 plate” means that linearly polarized light having a specific vibration direction is converted into linearly polarized light having a vibration direction orthogonal to the vibration direction of the linearly polarized light, or right circularly polarized light. Is converted to left circularly polarized light (or left circularly polarized light is converted to right circularly polarized light). Normally, two polarizers arranged in an orthogonal arrangement are unlikely to leak light from the front direction, but light leakage occurs in an oblique direction, and when the absorption axis of each polarizer is set to 0 ° and 90 °, 45 There is a tendency for the amount of light leakage to be maximum in the azimuth direction. The first optical element used in the present invention is used to reduce light leakage that occurs in the oblique direction of the liquid crystal display device and to increase the contrast ratio in the oblique direction.

  Further, the first optical element includes a stretched polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer, thereby reducing the absolute value of the photoelastic coefficient. Therefore, the liquid crystal panel and the liquid crystal display device having good display uniformity can be obtained by preventing the contraction stress of the polarizer and the shift and unevenness of the retardation value generated by the heat of the backlight.

D-1. Optical Characteristics of First Optical Element In this specification, Re [590] refers to an in-plane retardation value measured with light having a wavelength of 590 nm at 23 ° C. Re [590] represents the refractive index in the slow axis direction and the fast axis direction of the optical element (or retardation film) at a wavelength of 590 nm as nx and ny, respectively, and d (nm) as the optical element (or position). The thickness of the retardation film can be determined by the formula: Re [590] = (nx−ny) × d. The slow axis refers to the direction in which the in-plane refractive index is maximum.

  Re [590] of the first optical element used in the present invention is 200 nm to 350 nm, more preferably 220 nm to 320 nm, particularly preferably 240 nm to 300 nm, and most preferably 260 nm to 280 nm. By setting Re [590] to about ½ of the measurement wavelength, the contrast ratio in the oblique direction of the liquid crystal display device can be increased.

  Generally, the retardation value of an optical element (or retardation film) may change depending on the wavelength. This is called the wavelength dispersion characteristic of the retardation film. In the present specification, the chromatic dispersion characteristic can be obtained by a ratio of in-plane retardation values measured with light of wavelengths 480 nm and 590 nm at 23 ° C .: Re [480] / Re [590].

  Re [480] / Re [590] of the first optical element used in the present invention is preferably 0.8 to 1.2, more preferably 0.8 to 1.1, particularly preferably. 0.8-1.0. The smaller the value is within the above range, the more constant the phase difference value in the wide visible light region. Therefore, when used in a liquid crystal display device, the wavelength of light leaking is less likely to occur, and the liquid crystal display device The color shift amount in the oblique direction can be further reduced. In the present invention, the first optical element includes a stretched film of a polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer, so that a conventional aromatic resin can be obtained. Compared with a stretched polymer film having a main component, wavelength dispersion characteristics can be reduced. As a result, the color shift amount in the oblique direction of the liquid crystal display device can be further reduced.

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

  Rth [590] of the first optical element used in the present invention is preferably 100 nm to 175 nm, more preferably 110 nm to 160 nm in a range satisfying the formula: 0 nm <Rth [590] <Re [590]. And particularly preferably 120 nm to 150 nm, and most preferably 130 nm to 140 nm. By setting Re [590] to about 1/4 of the measurement wavelength, the contrast ratio in the oblique direction of the liquid crystal display device can be increased.

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

  In this specification, Rth [590] / Re [590] refers to a ratio between a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C. and an in-plane retardation value (also referred to as an Nz coefficient). .

  The Nz coefficient of the first optical element is greater than 0 and smaller than 1. That is, as the first optical element, one that satisfies 0 nm <Rth [590] <Re [590] is used. The first optical element can have a characteristic of nx> nz> ny by making the Nz coefficient more than 0 and less than 1. By setting the Nz coefficient in the above range, the phase difference value in the oblique direction is appropriately adjusted (for example, the angle dependency of the phase difference value is reduced), and the contrast ratio in the oblique direction of the liquid crystal display device can be increased. it can. The Nz coefficient of the first optical element is preferably 0.2 to 0.8, more preferably 0.3 to 0.7, and particularly preferably 0.4 to 0.6. Most preferably, the Nz coefficient of the first optical element is substantially 0.5. In the present specification, “substantially 0.5” includes the case where the Nz coefficient is 0.5 ± 0.05, preferably 0.5 ± 0.03, and particularly preferably 0.5 ± 0.02.

D-2. First Optical Element Arrangement Means Referring to FIGS. 1 and 2, as the method of arranging the first optical element 30 between the polarizer 21 and the liquid crystal cell 10, any appropriate method can be used depending on the purpose. Various methods can be adopted. Preferably, the first optical element 30 is provided with an adhesive layer or a pressure-sensitive adhesive layer on both sides thereof, and is adhered to the polarizer 21 and the liquid crystal cell 10. By filling the gap between the optical elements with the adhesive layer or the pressure-sensitive adhesive layer in this manner, the optical axes of the optical elements can be prevented from shifting when they are incorporated into a liquid crystal display device. Can be prevented from being rubbed and scratched. Further, the interface reflection in the gaps between the optical elements can be reduced, and the contrast ratio in the front direction and the oblique direction can be increased when used in a liquid crystal display device.

  The thickness of the adhesive layer or the pressure-sensitive adhesive layer can be appropriately determined within an appropriate range depending on the purpose of use and adhesive strength. The suitable thickness range of the adhesive layer is generally 0.01 μm to 50 μm, preferably 0.05 μm to 20 μm, and most preferably 0.1 μm to 10 μm. The suitable thickness range of the pressure-sensitive adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 80 μm, and most preferably 10 μm to 50 μm.

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

  Preferably, the first optical element 30 is arranged so that its slow axis is substantially parallel or orthogonal to the absorption axis of the polarizer 21. Most preferably, the first optical element 30 is arranged such that its slow axis is substantially parallel to the absorption axis of the polarizer 21. This is because a roll-shaped optical element in which the first optical element 40 and the polarizer 21 are laminated can be manufactured according to such a form, and productivity can be greatly improved. In this specification, “substantially parallel” means that the angle formed by the slow axis of the first optical element 30 and the absorption axis of the first polarizer 21 is 0 ° ± 2.0 °. In some cases, it is preferably 0 ° ± 1.0 °, more preferably 0 ° ± 0.5 °. The term “substantially orthogonal” includes the case where the angle formed by the slow axis of the first optical element 30 and the absorption axis of the first polarizer 21 is 90 ° ± 2.0 °. The angle is preferably 90 ° ± 1.0 °, more preferably 90 ° ± 0.5 °. As the degree of deviation from these angular ranges increases, the contrast ratio in the front and oblique directions tends to decrease when used in a liquid crystal display device.

D-3. Configuration of First Optical Element The configuration (lamination configuration) of the first optical element is not particularly limited as long as it satisfies the optical characteristics described in the above section D-1. Specifically, the first optical element may be a retardation film alone or may be a laminate of two or more retardation films, and a retardation film and another film (preferably, etc. A laminate with an isotropic film). Preferably, the first optical element is a single retardation film.

  FIG. 4 is a schematic perspective view illustrating a representative example of a preferred embodiment of the first optical element including a relationship with an absorption axis of a polarizer. 4A and 4B show a case where the first optical element is a single retardation film 31. FIG. The retardation film 31 in FIG. 4A is arranged so that its slow axis is parallel to the absorption axis of the polarizer 21. The retardation film 31 in FIG. 4B is arranged so that its slow axis is orthogonal to the absorption axis of the polarizer 21. If it is such a form, a retardation film will serve as the protective layer by the side of the liquid crystal cell of a polarizer, and it can contribute to thickness reduction of a liquid crystal panel. FIG. 4C shows a case where the first optical element 30 is a laminate of a retardation film 31 and an isotropic film 32. According to such a form, the isotropic film 32 is interposed, so that the contraction stress of the polarizer and the heat of the backlight are prevented from propagating to the retardation film 31, so that the liquid crystal panel is more excellent in optical uniformity. Can be obtained. In the illustrated example, the case where the slow axis of the retardation film is perpendicular to the absorption axis of the polarizer is shown, but this may be parallel. FIG. 4D shows a case where the first optical element 30 is a laminate of a retardation film 33 and a retardation film 34. The retardation film 33 and the retardation film 34 are arranged so that their slow axes are parallel to each other. In the illustrated example, the case where the slow axis of the retardation film is parallel to the absorption axis of the polarizer is shown, but this may be orthogonal. In addition, when a 1st optical element is a laminated body, an adhesive bond layer and an adhesive layer (all are not shown) may be included. When the laminate includes two or more retardation films, these retardation films may be the same or different. The details of the retardation film will be described later in the section D-4, and the isotropic film will be described later in the section F.

  Re [590] of the retardation film used in the first optical element can be appropriately selected depending on the number of retardation films used. For example, when the first optical element is composed of only one retardation film, Re [590] of the retardation film is preferably equal to Re [590] of the first optical element. Therefore, it is preferable that the retardation value of the pressure-sensitive adhesive layer or the adhesive layer used when the first optical element is laminated on a polarizer or a liquid crystal cell is as small as possible. For example, when the first optical element is a laminate including two or more retardation films, the sum of Re [590] of the respective retardation films is the Re [590] of the first optical element. It is preferable to design so that it becomes equal to]. Specifically, two retardation films are laminated so that their slow axes are parallel to each other, and a first optical element having an Nz coefficient of 0.5 and Re [590] of 270 nm is obtained. When manufactured, Re [590] of the retardation film having an Nz coefficient of 0.5 can be set to 135 nm, respectively. Here, for the sake of simplicity, only the case where the number of retardation films is two or less is shown, but it goes without saying that the present invention can also be applied to a laminate including three or more retardation films.

  The total thickness of the first optical element is preferably 20 μm to 400 μm, more preferably 30 μm to 300 μm, and most preferably 40 μm to 200 μm. By setting the first optical element in the above thickness range, it is possible to obtain a thin liquid crystal panel having a practically sufficient mechanical strength.

D-4. Retardation film used for first optical element The retardation film used for the first optical element is a polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer. A stretched film is used. In this specification, “stretched film” means a plastic film in which tension is applied to an unstretched film at an appropriate temperature, or tension is further applied to a previously stretched film to increase molecular orientation in a specific direction. Say. A polymer film composed mainly of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer is more likely to cause a phase difference due to stretching than a polymer film mainly composed of other aliphatic resins. The absolute value of the photoelastic coefficient is smaller than that of a polymer film containing an aromatic resin as a main component. One of the great achievements of the present invention is actually a retardation film having a small photoelastic coefficient, a relationship of nx>nz> ny, and satisfying the above formulas (1) and (2). It is that it was made.

  The thickness of the retardation film can be appropriately selected according to the laminated structure and purpose of the first optical element. Preferably they are 20 micrometers-200 micrometers, More preferably, they are 30 micrometers-180 micrometers, Most preferably, they are 40 micrometers-150 micrometers. Within the above range, a retardation film excellent in mechanical strength and optical uniformity and satisfying the optical characteristics described in the above section D-1 can be obtained.

The absolute value (C [590] (m ² / N)) of the photoelastic coefficient of the retardation film is preferably 1 × 10 ^{−12 to} 100 × 10 ⁻¹² , and more preferably 1 × 10 ⁻¹² to 60 × 10 ⁻¹² , particularly preferably 1 × 10 ⁻¹² to 30 × 10 ⁻¹² , and most preferably 1 × 10 ⁻¹² to 8 × 10 ⁻¹² . The smaller the absolute value of the photoelastic coefficient, the better the display uniformity by preventing the shift and unevenness of the retardation value caused by the contraction stress of the polarizer and the heat of the backlight when used in a liquid crystal display device. A liquid crystal panel and a liquid crystal display device can be obtained.

  The transmittance of the retardation film measured with light having a wavelength of 590 nm at 23 ° C. is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. The second optical element preferably has a similar light transmittance.

  The cycloolefin resin obtained by hydrogenating the ring-opening polymer of the norbornene-based monomer can be obtained by subjecting the norbornene-based monomer to a metathesis reaction to obtain a ring-opening polymer, and further hydrogenating the ring-opening polymer. it can. For example, NTS Co., Ltd. “Optical polymer material development and application technology” p. 103-p. 111 (2003 edition) and the method described in paragraphs [0035] to [0037] of JP-A-2001-350017.

Examples of the ring-opening polymerization catalyst used in the metathesis reaction include metal halides such as ruthenium, rhodium, palladium, osmium, iridium and platinum; a polymerization catalyst comprising a nitrate or acetylacetone compound and a reducing agent; or titanium And a polymerization catalyst comprising a metal halide such as vanadium, zirconium, tungsten, molybdenum, or an acetylacetone compound and an organoaluminum compound. The reaction conditions such as polymerization temperature and pressure can be appropriately selected according to the kind of norbornene-based monomer and the target molecular weight, but the polymerization temperature is preferably in the range of −50 ° C. to 100 ° C., and the range of the polymerization pressure. Is preferably 0 to 50 kgf / cm ² .

  The hydrogenated cycloolefin resin can be obtained by a hydrogenation reaction performed by blowing hydrogen in the presence of a known hydrogenation catalyst. Specific examples of the hydrogenation catalyst include transition metals such as cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, titanocene dichloride / n-butyllithium, zirconocene dichloride / sec-butyllithium, and tetrabutoxytitanate / dimethylmagnesium. Homogeneous catalyst comprising a combination of compound / alkyl metal compound; heterogeneous metal catalyst such as nickel, palladium, platinum, etc .; nickel / silica, nickel / diatomaceous earth, nickel / alumina, palladium / carbon, palladium / silica, palladium / Examples thereof include a heterogeneous solid supported catalyst in which a metal catalyst such as diatomaceous earth or palladium / alumina is supported on a support.

  As said norbornene-type monomer, a suitable thing can be selected suitably from a conventionally well-known thing. Specific examples include norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5, 5-dimethyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl-2-norbornene, 5-phenyl-5-methyl-2-norbornene, ethylene -Tetracyclododecene copolymer, 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4 : 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4: 5,8-ethylidene 1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a- Octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8- Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8 , 8a-octahydronaphthalene, 1,4-dimethano-1,4,4a, 4b, 5,8,8a, 9a-octahydrofluorene, 5,8-methano-1,2,3,4,4a, 5 , 8,8a-octahydro-2.3-cyclopentadienonaphthalene, 4,9: 5 -Dimethano-3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentanthracene and the like. The norbornene-based monomers can be used alone or in combination of two or more. The norbornene-based monomer can be used after any appropriate modification.

The hydrogenation rate of the cycloolefin resin obtained by hydrogenating the ring-opening polymer of the norbornene monomer is usually 90% or more from the viewpoint of heat deterioration resistance and light deterioration resistance. Preferably it is 95% or more, More preferably, it is 99% or more. The hydrogenation rate can be determined from the respective integrated intensity ratios of paraffinic hydrogen and olefinic hydrogen by measuring ¹ H-NMR (500 MHz) of the resin.

  The weight average molecular weight (Mw) of the cycloolefin resin obtained by hydrogenating the ring-opening polymer of the norbornene monomer is a value measured by a gel permeation chromatography (GPC) method using a tetrahydrofuran solvent, preferably 20, The range is from 000 to 400,000, more preferably from 30,000 to 300,000, and most preferably from 40,000 to 200,000. When the weight average molecular weight is in the above range, a material having excellent mechanical strength, good solubility, moldability, and casting operability can be obtained.

  Any appropriate forming method can be used as a method for obtaining a polymer film mainly composed of a cycloolefin resin obtained by hydrogenating the ring-opening polymer of the norbornene monomer. For example, an appropriate one can be appropriately selected from compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, solvent casting, and the like. Among these molding methods, the extrusion molding method or the solvent casting method is particularly preferable. This is because the smoothness of the resulting polymer film can be improved and good optical uniformity (for example, a retardation value that is uniform in the plane and in the thickness direction) can be obtained.

  Specifically, the extrusion molding method involves heating and melting a resin composition containing a resin as a main component, a plasticizer, an additive, etc., and then using a T-die or the like to form a substrate (supporting material) The film is produced by extruding it into a thin film on the surface of the body and cooling it. Specifically, the solvent casting method is a method in which a concentrated solution (dope) obtained by dissolving a resin composition containing a resin, a plasticizer, an additive and the like as a main component in a solvent is removed, and an endless stainless belt, a rotating drum surface, This is a method for producing a film by uniformly casting a thin film on the surface of a substrate (also referred to as a support) such as a polymer film (for example, PET film) and evaporating the solvent.

  The conditions adopted at the time of molding a polymer film mainly composed of a cycloolefin resin obtained by hydrogenating the ring-opening polymer of the norbornene monomer can be appropriately selected depending on the composition and type of the resin and the molding process. In the case of the above-described extrusion molding method, there is no particular limitation, but the extrusion method is preferably a method using a T die, the resin temperature is 240 ° C to 300 ° C, and the temperature of the take-up roll (cooling drum) is 100 ° C to It is preferable to set the temperature to 150 ° C. and gradually cool from a high temperature. In the case of the solvent casting method described above, there is no particular limitation, but preferred solvents include cyclopentanone, cyclohexanone, methyl isobutyl ketone, toluene, ethyl acetate, dichloromethane, chloroform, tetrahydrofuran and the like. The drying temperature of the solvent is preferably 50 ° C. to 250 ° C., more preferably 80 ° C. to 150 ° C., and it is preferable that the temperature is gradually raised from a low temperature and dried. By selecting such conditions, a retardation film with high optical uniformity can be obtained.

  The polymer film containing as a main component a cycloolefin resin obtained by hydrogenating the ring-opening polymer of the norbornene monomer may further contain any appropriate additive. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, ultraviolet absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, and thickeners. Etc. The kind and amount of the additive used can be appropriately set according to the purpose. For example, the content of the additive is preferably 10 (weight ratio) to 0.01 (weight ratio), more preferably 8 (weight ratio) to 0, based on the total solid content 100 of the polymer film. 0.05 (weight ratio), and most preferably 5 (weight ratio) to 0.1 (weight ratio).

  In addition to the above-described polymer film, a commercially available optical film can be used as it is as the polymer film containing as a main component a cycloolefin resin obtained by hydrogenating the ring-opening polymer of the norbornene monomer. Further, a commercially available optical film may be used after being subjected to secondary processing such as stretching / relaxation. As an example of a polymer film mainly composed of a cycloolefin-based resin obtained by hydrogenating a ring-opening polymer of a commercially available norbornene-based monomer, a trade name “ZEONEX Series” (480, 480R, etc.) manufactured by Nippon Zeon Co., Ltd. The product name “Zeonor series” (ZF14, ZF16, etc.) manufactured by the same company, and the product name “Arton series” (ARTON G, ARTON F, etc.) manufactured by JSR Co., Ltd. can be mentioned.

  The retardation film used for the first optical element is obtained by, for example, bonding a shrinkable film on both sides of a polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer. It can be obtained by heating and stretching with a roll stretching machine by a longitudinal uniaxial stretching method. The shrinkable film is used for imparting a shrinkage force in a direction perpendicular to the stretching direction at the time of heat stretching and increasing a refractive index (nz) in the thickness direction. The method for attaching the shrinkable film on both sides of the polymer film is not particularly limited, but an acrylic pressure-sensitive adhesive layer having an acrylic polymer as a base polymer between the polymer film and the shrinkable film. The method of providing and bonding is preferable from the viewpoint of excellent workability and economical efficiency.

  An example of a method for producing a retardation film used in the first optical element will be described with reference to FIG. FIG. 5 is a schematic diagram showing a concept of a typical production process of a retardation film used for the first optical element. For example, a polymer film 302 mainly composed of a cycloolefin-based resin obtained by hydrogenating a ring-opening polymer of a norbornene-based monomer is unwound from the first unwinding portion 301 and is laminated by the laminating rolls 307 and 308. A shrinkable film 304 having an adhesive layer fed from the second feeding portion 303 and a shrinkable film 306 having an adhesive layer drawn from the third feeding portion 305 are bonded to both surfaces of 302. The The polymer film having the shrinkable film attached to both sides is given a tension in the longitudinal direction of the film by rolls 310, 311, 312 and 313 having different speed ratios while being held at a constant temperature by the temperature control means 309 ( At the same time, when the shrinkable film shrinks, tension is applied to the polymer film in the thickness direction as well. The stretched film 318 is wound up by the third winding unit 319 after the shrinkable films 315 and 317 are peeled off together with the adhesive layer at the first and second winding units 314 and 316. .

  The shrinkable film has a shrinkage ratio in the film longitudinal direction at 140 ° C .: S (MD) of 2.7% to 9.4%, and a shrinkage ratio in the width direction: S (TD) of 4.6. What is% to 15.8% is preferably used. Further, the shrinkable film has a difference between the shrinkage in the width direction and the shrinkage in the longitudinal direction: ΔS = S (TD) −S (MD) in the range of 3.2% to 9.6%. preferable. If it is said range, it will be excellent in optical uniformity and the retardation film which satisfies the optical characteristic as described in said D-1 term can be obtained.

  The shrinkage rates S (MD) and S (TD) can be determined in accordance with the heating shrinkage rate A method of JIS Z 1712-1997 (however, the heating temperature is set to 140 ° C. instead of 120 ° C.). The difference is that a load of 3 g was applied). Specifically, five test pieces each having a width of 20 mm and a length of 150 mm were taken from the vertical (MD) and horizontal (TD) directions, and a test piece with a mark at a distance of about 100 mm at the center was prepared. To do. The test piece is suspended vertically in an air circulation drying oven maintained at a temperature of 140 ° C. ± 3 ° C. with a load of 3 g, heated for 15 minutes, taken out, and left in a standard state (room temperature) for 30 minutes. Then, using a caliper specified in JIS B 7507, the distance between the gauge points was measured to obtain an average value of the five measured values, and S (%) = [[distance between gauge points before heating ( mm) −distance between gauge points after heating (mm)] / distance between gauge points before heating (mm)] × 100.

  The shrinkable film is preferably a stretched film such as a biaxially stretched film or a uniaxially stretched film. The shrinkable film can be obtained, for example, by stretching an unstretched film formed into a sheet by an extrusion method in the longitudinal and / or transverse direction at a predetermined magnification with a simultaneous biaxial stretching machine or the like. The molding and stretching conditions can be appropriately selected depending on the composition, type and purpose of the resin used.

  Examples of the material for forming the shrinkable film include polyester, polystyrene, polyethylene, polypropylene, polyvinyl chloride, and polyvinylidene chloride. Among these, as the shrinkable film used in the present invention, a biaxially stretched polypropylene film is preferably used in view of excellent mechanical strength, thermal stability, surface uniformity and the like.

  In addition, the shrinkable film can be used for general packaging, food packaging, pallet packaging, shrinkage label, cap seal, and electrical insulation as long as the object of the present invention is satisfied. A commercially available shrinkable film can be appropriately selected and used. These commercially available shrinkable films may be used as they are, or after being subjected to secondary processing such as stretching treatment or shrinkage treatment. Specific examples of commercially available shrinkable films include Oji Paper Co., Ltd. product name “Alphan Series”, Gunze Co., Ltd. product name “Fancy Top Series”, and Toray Industries, Inc. product name “Trephan Series”. , Santox Co., Ltd., trade name “Santox-OP Series”, Tosero Co., Ltd., trade name “Tosero OP Series”, and the like.

  Temperature in temperature control means (also referred to as stretching temperature) when heat-stretching a laminate of a polymer film composed mainly of a cycloolefin resin hydrogenated with a ring-opening polymer of a norbornene monomer and a shrinkable film Can be appropriately selected according to the target retardation value, the type and thickness of the polymer film used, and the like. Preferably, it is performed in the range of Tg + 1 ° C. to Tg + 30 ° C. with respect to the glass transition point (Tg) of the polymer film. This is because the retardation value tends to be uniform, and the film is difficult to crystallize (white turbidity). More specifically, the stretching temperature is preferably 110 ° C to 185 ° C, more preferably 120 ° C to 170 ° C, and most preferably 130 ° C to 160 ° C. The glass transition temperature (Tg) can be determined by a DSC method according to JIS K 7121-1987.

  The temperature control means is not particularly limited, but is an air circulation type constant temperature oven through 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. A known heating method and temperature control method using a belt or the like can be given.

  Further, the stretching ratio (stretching ratio) when stretching a laminate of a polymer film mainly composed of a cycloolefin-based resin hydrogenated with a ring-opening polymer of a norbornene-based monomer and a shrinkable film is The phase difference value to be selected, the type and thickness of the polymer film to be used, and the like can be appropriately selected. The draw ratio is preferably 1.05 times to 1.7 times, and more preferably 1.05 times to 1.50 times. The feed rate during stretching is not particularly limited, but is preferably 0.5 m / min to 30 m / min, more preferably 1 m / min to 20 m / min from the mechanical accuracy and stability of the stretching apparatus. If it is said extending | stretching conditions, not only the optical characteristic of the said D-1 term can be satisfied, but the retardation film excellent in optical uniformity can be obtained.

E. Second Optical Element Referring to FIGS. 1 and 2, the second optical element 40 is disposed between the liquid crystal cell 10 and the polarizer 22. According to such a configuration, the second optical element functions as a protective layer on the liquid crystal cell side of the polarizer, preventing the polarizer from being deteriorated, and as a result, the display characteristics of the liquid crystal display device can be improved for a long time. Can be maintained. The second optical element 40 is substantially optically negative uniaxial. In this specification, “substantially optically negative uniaxiality” means that the in-plane main refractive index is nx, ny, and the refractive index in the thickness direction is nz, and the refractive index distribution is nx. = Satisfies ny> nz. An optical element having negative uniaxiality ideally has an optical axis in the normal direction. In the present specification, nx, ny and nz include not only the case where they are completely the same, but also the case where nx, ny and nz are substantially the same. Here, “when nx, ny and nz are substantially the same” means, for example, that the in-plane retardation value (Re [590]) is 10 nm or less and the thickness direction retardation value (Rth [ 590]) having an absolute value of 10 nm or less.

  In the present invention, the second optical element is for optically compensating and canceling a retardation value of a liquid crystal cell including a liquid crystal layer including a nematic liquid crystal aligned in a homeotropic alignment in the absence of an electric field. Used. FIG. 6 is a typical conceptual diagram illustrating a method of canceling the phase difference value of the liquid crystal cell using the second optical element. In the present specification, “cancel the retardation value of the liquid crystal cell” means that the laminated body of the liquid crystal cell and the optical element has an isotropic refractive index distribution substantially having a relationship of nx = ny = nz. It means to compensate optically. As shown in FIG. 6, for example, a liquid crystal cell having a refractive index distribution of nz> nx = ny (that is, a liquid crystal cell including a liquid crystal layer including nematic liquid crystal aligned in a homeotropic alignment in the absence of an electric field) In order to cancel the phase difference value of), preferably, a second optical element having a refractive index distribution exhibiting a relationship of nx = ny> nz is disposed. Here, the second optical element having a relationship of nx = ny> nz can be rephrased as an optical element satisfying 0 nm ≦ Re [590] ≦ 10 nm and Rth [590]> 10 nm.

E-1. Optical characteristics of the second optical element Re [590] of the second optical element is preferably 0 nm to 10 nm, more preferably 0 nm to 5 nm, and most preferably 0 nm to 3 nm. By setting it as said range, the contrast ratio of the front of a liquid crystal display device and a diagonal direction can be made high.

  As the Rth [590] of the second optical element, those exceeding 10 nm are used in order to cancel Rth [590] of the liquid crystal cell. For a normally black mode liquid crystal cell that is in a dark state (black display) when a low voltage is applied, the phase difference value of the liquid crystal cell when the low voltage is applied may be canceled. Rth [590] of the second optical element is preferably 100 nm to 800 nm, more preferably 150 nm to 600 nm, and most preferably 200 nm to 500 nm. By setting it as said range, the contrast ratio of the diagonal direction of a liquid crystal display device can be made high.

  The wavelength dispersion characteristic of an optical element having optically negative uniaxiality is as follows. The ratio of retardation values measured by injecting light having wavelengths of 480 nm and 590 nm at an angle of 40 ° from the sample plane at 23 ° C .: R40 [480 ] / R40 [590].

  R40 [480] / R40 [590] of the second optical element used in the present invention is preferably equal to R40 [480] / R40 [590] of the liquid crystal cell. Specifically, it is preferably 0.8 to 2.0, more preferably 1.0 to 1.8, and particularly preferably 1.1 to 1.6. The closer the value of R40 [480] / R40 [590] of the second optical element is to the value of R40 [480] / R40 [590] of the liquid crystal cell, the larger the phase difference value of the liquid crystal cell in the visible light region. Therefore, light leakage can be further reduced, and as a result, the contrast ratio in the oblique direction of the liquid crystal display device can be further increased. In addition, the wavelength of the light leaking is less likely to occur, and as a result, the amount of color shift in the oblique direction of the liquid crystal display device can be further reduced. In the present invention, for example, when the second optical element includes a retardation film made of a polymer film containing polyimide as a main component, the wavelength dispersion characteristic of the second optical element and the wavelength dispersion characteristic of the liquid crystal cell. Can be made substantially equal, so that when used in a liquid crystal display device, the color shift amount in the oblique direction can be further reduced. The retardation film used for the second optical element will be described later in the section E-4.

E-2. Referring to FIGS. 1 and 2, the method of arranging the second optical element 40 between the liquid crystal cell 10 and the polarizer 22 is arbitrarily appropriate depending on the purpose. Various methods can be adopted. Preferably, the second optical element 40 is provided with an adhesive layer or a pressure-sensitive adhesive layer on both sides thereof, and is adhered to the liquid crystal cell 10 and the polarizer 22. By filling the gap between the optical elements with the adhesive layer or the pressure-sensitive adhesive layer in this manner, the optical axes of the optical elements can be prevented from shifting when they are incorporated into a liquid crystal display device. Can be prevented from being rubbed and scratched. Further, the interface reflection in the gaps between the optical elements can be reduced, and the contrast ratio in the front direction and the oblique direction can be increased when used in a liquid crystal display device.

  The thickness of the adhesive layer or the pressure-sensitive adhesive layer and the type of the adhesive or pressure-sensitive adhesive forming the adhesive layer or the pressure-sensitive adhesive layer are the same as those described in the above section D-2, and the same ones. Can be employed.

  When the nx and ny are completely the same, the second optical element 40 has no in-plane retardation value, so that the slow axis is not detected and is arranged regardless of the absorption axis of the polarizer 22. Can be done. Even if nx and ny are substantially the same, a slow axis may be detected if nx and ny are slightly different. When the slow axis is detected, the second optical element 40 is preferably arranged so that the slow axis is substantially parallel or orthogonal to the absorption axis of the polarizer 22. In this specification, “substantially parallel” means that the angle formed by the slow axis of the second optical element 40 and the absorption axis of the polarizer 22 is 0 ° ± 2.0 °. Included, preferably 0 ° ± 1.0 °, most preferably 0 ° ± 0.5 °. “Substantially orthogonal” includes the case where the angle formed by the slow axis of the second optical element 40 and the absorption axis of the polarizer 22 is 90 ° ± 2.0 °, preferably 90 °. It is ± 1.0 °, and more preferably 90 ° ± 0.5 °. As the degree of deviation from these angular ranges increases, the contrast ratio in the front and oblique directions tends to decrease when used in a liquid crystal display device.

E-3. Configuration of Second Optical Element The configuration (laminate configuration) of the second optical element is not particularly limited as long as it satisfies the optical characteristics described in the above section E-1. Specifically, the second optical element may be a retardation film alone or a laminate of two or more retardation films, and the retardation film and other films (preferably, etc. A laminate with an isotropic film). Preferably, the second optical element is a single retardation film or a laminate including at least one retardation film and including two films.

  FIG. 7 is a schematic perspective view illustrating a representative example of a preferred embodiment of the second optical element including a relationship with an absorption axis of a polarizer. FIG. 7A shows a case where the second optical element is a single retardation film 41 (a retardation film has substantially optically negative uniaxiality). If it is such a form, a phase difference film will serve as the protective layer by the side of the liquid crystal cell of a polarizer, and can contribute to thickness reduction of a liquid crystal panel. FIG. 7B shows a case where the second optical element 40 is a laminate of a retardation film 41 and an isotropic film 43. Preferably, the isotropic film 43 is disposed between the retardation film 41 and the polarizer 22. According to such a configuration, the isotropic film 43 is interposed, so that the contraction stress of the polarizer and the heat of the backlight are prevented from propagating to the retardation film 41, so that the liquid crystal panel is more excellent in optical uniformity. Can be obtained. FIG. 7C shows a case where the film is a laminate of a retardation film 43 and a retardation film 44 (all of the retardation films have substantially optically negative uniaxiality). FIG.7 (d) shows the case where it is a laminated body of the phase difference film 45 and the phase difference film 46 (all phase difference films have in-plane phase difference value). The retardation film 45 and the retardation film 46 are disposed so that their slow axes are orthogonal to each other. According to such a form, Re [590] can be reduced. In the case where the second optical element is a laminate, an adhesive layer, a pressure-sensitive adhesive layer, an anchor coat layer, or the like (none of which is shown) may be included for bonding the films together. When the laminate includes two or more retardation films, these retardation films may be the same or different. If it is said form, not only the optical characteristic of the said E-1 term can be satisfied, but the optical element excellent in optical uniformity can be obtained. The details of the retardation film will be described later in Section E-4, and the isotropic film will be described in Section F.

  Rth [590] of the retardation film used in the second optical element can be appropriately selected depending on the number of retardation films used. For example, when the second optical element is composed of a retardation film alone, it is preferable that Rth [590] of the retardation film is equal to Rth [590] of the second optical element. Therefore, it is preferable that the retardation value of the pressure-sensitive adhesive layer or the adhesive layer used when the second optical element is laminated on a polarizer or a liquid crystal cell is as small as possible. For example, when the second optical element is a laminate including two or more retardation films, the sum of Rth [590] of each retardation film is equal to Rth [590] of the second optical element. It is preferable to design so that it becomes equal to]. Specifically, when two retardation films are laminated to produce a second optical element having Rth [590] of 400 nm, Rth [590] of the retardation film is set to 200 nm, respectively. be able to. At this time, when the two retardation films have in-plane retardation values (Re [590]), in order to reduce Re [590] as the laminate, preferably each of the retardation films Re [590] is set to be equal and the slow axes are arranged to be orthogonal. Here, for the sake of simplicity, only the case where the number of retardation films is two or less is shown, but it goes without saying that the present invention can also be applied to a laminate including three or more retardation films.

  The total thickness of the second optical element is preferably 2 μm to 400 μm, more preferably 2 μm to 200 μm, and most preferably 2 μm to 100 μm. By setting the second optical element in the above thickness range, a thin liquid crystal panel having practically sufficient mechanical strength can be obtained.

E-4. The retardation film used for the second optical element The retardation film used for the second optical element is not particularly limited, but is excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like. Therefore, a material that hardly causes optical unevenness is preferably used.

  The thickness of the retardation film can be appropriately selected according to the laminated structure and purpose of the first optical element. Preferably they are 1 micrometer-30 micrometers, More preferably, they are 2 micrometers-20 micrometers, Especially preferably, they are 3 micrometers-15 micrometers, Most preferably, they are 5 micrometers-12 micrometers. If it is said range, it will be excellent in mechanical strength and optical uniformity, and the retardation film which satisfies the optical characteristic as described in said E-1 term can be obtained. Furthermore, by reducing the thickness of the retardation film, even if a material with a large absolute value of the photoelastic coefficient is used, a shift or unevenness in the retardation value caused by the contraction stress of the polarizer or the heat of the backlight is prevented, and the film is excellent. A liquid crystal panel and a liquid crystal display device having display uniformity can be obtained.

  The difference between the in-plane main refractive index (nx) and the refractive index (nz) in the thickness direction (also referred to as birefringence in the thickness direction (Δnxz)) of the retardation film is preferably 0.03 to 0.20. More preferably, it is 0.04-0.15, Most preferably, it is 0.05-0.12, Most preferably, it is 0.06-0.10. By setting it as said range, the single phase difference film which satisfies the said E-1 term can be obtained, and thickness can be made thin. The above Δnxz can be adjusted by appropriately selecting the type of resin or solvent used and the drying conditions. Specifically, Δnxz can be increased by selecting a rigid molecular structure, and Δnxz can be decreased by selecting a flexible one.

The absolute value (C [590] (m ² / N)) of the photoelastic coefficient of the retardation film is preferably 1 × 10 ^{−12 to} 100 × 10 ⁻¹² , and more preferably 1 × 10 ⁻¹² to 90 × 10 ⁻¹² , particularly preferably 1 × 10 ⁻¹² to 80 × 10 ⁻¹² . The smaller the absolute value of the photoelastic coefficient, the better the display uniformity, preventing the shift and unevenness of the retardation value generated by the contraction stress of the polarizer and the heat of the backlight when used in a liquid crystal display device. A panel and a liquid crystal display device can be obtained.

  The transmittance of the retardation film measured with light having a wavelength of 590 nm at 23 ° C. is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. The second optical element preferably has a similar light transmittance.

  The retardation film is preferably a polymer film mainly composed of a thermoplastic resin. The thermoplastic resin may be an amorphous polymer or a crystalline polymer. Amorphous polymers have the advantage of excellent transparency, and crystalline polymers have the advantage of excellent rigidity, strength, and chemical resistance. The polymer film containing the thermoplastic resin as a main component may be stretched or not stretched.

  Examples of the thermoplastic resin include polyethylene, polypropylene, polynorbornene, polyvinyl chloride, cellulose ester, polystyrene, ABS resin, AS resin, polymethyl methacrylate, polyvinyl acetate, and polyvinylidene chloride; polyamide, polyacetal, General-purpose engineering plastics such as polycarbonate, modified polyphenylene ether, polybutylene terephthalate, and polyethylene terephthalate; Super such as polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyarylate, liquid crystal polymer, polyamideimide, polyimide, and polytetrafluoroethylene Examples include engineering plastics. Said thermoplastic resin is used individually or in combination of 2 or more types. The thermoplastic resin can be used after any appropriate polymer modification. Examples of the polymer modification include modifications such as copolymerization, crosslinking, molecular terminals, and stereoregularity. Particularly preferred as the retardation film used in the second optical element is a polymer film containing polyimide as a main component. Polyimide is a process of evaporation of the solvent when the polyimide solution is applied to the surface of the base material (also called a support) and dried. A retardation film having a large birefringence in the thickness direction can be obtained without requiring secondary processing.

  As a method for obtaining the polymer film containing the thermoplastic resin as a main component, a method similar to the molding method described in the above section D-4 can be employed. Moreover, the conditions adopted at the time of molding can be appropriately selected depending on the composition and type of the resin and the molding process.

Any appropriate polyimide can be adopted as the polyimide. Specific examples include aromatic polyimide, thermoplastic polyimide, thermosetting polyimide, fluorine-containing polyimide, photosensitive polyimide, alicyclic polyimide, liquid crystalline polyimide, and polysiloxane block polyimide. These polyimides may be used alone or in combination of two or more. Furthermore, the resin composition etc. which blended polyamic acid which is a precursor of a polyimide and a polyimide can also be used. Among these, in the present invention, fluorine-containing polyimide is preferably used because it is excellent in transparency and a target retardation value in the thickness direction can be thinly obtained. In the present specification, “fluorinated polyimide” refers to C such as —CF ₂ — group or —CF ₃ group in the molecule (one or both of tetracarboxylic dianhydride moiety and diamine moiety). It has a -F bond. Specific examples of the fluorine-containing polyimide include “latest polyimide” p. 274-p. And polyimide disclosed in H.275 (2002 edition).

  The polyimide can be typically obtained by reaction of tetracarboxylic dianhydride and diamine. Arbitrary appropriate methods may be employ | adopted as a method of making the said tetracarboxylic dianhydride and diamine react. For example, chemical imidization that proceeds in two steps may be used, or thermal imidization that proceeds in one step.

  As a specific example of the above chemical imidation, diamine is dissolved in a polar amide solvent such as dimethylacetamide or N-methylpyrrolidone, and tetracarboxylic dianhydride is added to this solution as a solid at room temperature. Upon stirring, the solid tetracarboxylic dianhydride dissolves, and a ring-opening polymerization addition reaction takes place with the diamine with heat generation, increasing the viscosity of the polymerization solution and producing polyamic acid (first step) ). Next, there is a method in which a dehydrating agent such as acetic anhydride is added to the reaction solution containing the polyamic acid and heated to cause a dehydration cyclization reaction to generate polyimide (second step).

  As a specific example of the thermal imidization, a diamine, tetracarboxylic dianhydride, and isoquinoline (catalyst) are dissolved in a high-boiling organic solvent such as m-cresol in a reaction vessel equipped with a Dean-Stark apparatus. When the solution is heated at 175 to 180 ° C. while stirring, a method in which a dehydration cyclization reaction occurs and a polyimide is generated can be mentioned.

  Specific examples of the tetracarboxylic dianhydride that is a starting material for the polyimide used in the present invention include pyromellitic dianhydride, 3,6-diphenylpyromellitic dianhydride, 3,6-bis (trifluoromethyl) ) Pyromellitic dianhydrides such as pyromellitic dianhydride, 3,6-dibromopyromellitic dianhydride, 3,6-dichloropyromellitic dianhydride; 3,3 ′, 4,4′-benzophenone Benzophenone tetracarboxylic dianhydrides such as tetracarboxylic dianhydride, 2,3,3 ', 4'-benzophenone tetracarboxylic dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic dianhydride 2,3,6,7-naphthalene-tetracarboxylic dianhydride, 1,2,5,6-naphthalene-tetracarboxylic dianhydride, 2,6-dichloro-naphthalene Naphthalene-based tetracarboxylic dianhydrides such as 1,4,5,8-tetracarboxylic dianhydride; thiophene-2,3,4,5-tetracarboxylic dianhydride, pyrazine-2,3,5 Heterocyclic aromatic tetracarboxylic dianhydrides such as 6-tetracarboxylic dianhydride and pyridine-2,3,5,6-tetracarboxylic dianhydride; 2,2'-dibromo-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-dichloro-4,4', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-bis (trifluoromethyl) ) -4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, etc. 2,2'-substituted biphenyltetracarboxylic dianhydride; 3,3', 4,4'-biphenyltetracarboxylic dianhydride Anhydride, bis (2,3-dicarboxy Enyl) methane dianhydride, bis (2,5,6-trifluoro-3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1, 1,3,3,3-hexafluoropropane dianhydride, 4,4'-bis (3,4-dicarboxyphenyl) -2,2-diphenylpropane dianhydride, bis (3,4-dicarboxyphenyl) ) Ether dianhydride, 4,4'-oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfonic dianhydride, 3,3 ', 4,4'-diphenylsulfone tetracarboxylic dianhydride , 4,4 '-[4,4'-isopropylidene-di (p-phenyleneoxy)] bis (phthalic anhydride), N, N- (3,4-dicarboxyphenyl) -N-methylamine Dianhydride, bis (3 , 4-dicarboxyphenyl) diethylsilane dianhydride and the like, but not limited thereto. The tetracarboxylic dianhydride containing a C—F bond includes 3,6-bis (trifluoromethyl) pyromellitic dianhydride, 2,2′-bis (trifluoromethyl) -4,4 ′, 5,5'-biphenyltetracarboxylic dianhydride, bis (2,5,6-trifluoro-3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) ) -1,1,1,3,3,3-hexafluoropropane dianhydride and the like.

  Specific examples of the diamine which is a starting material for the polyimide used in the present invention include o-, m- and p-phenylenediamine, 2,4-diaminotoluene, 1,4-diamino-2-methoxybenzene, 1 Benzenediamines such as 1,4-diamino-2-phenylbenzene and 1,3-diamino-4-chlorobenzene; diaminobenzophenones such as 2,2′-diaminobenzophenone and 3,3′-diaminobenzophenone; 1,8-diamino Naphthalene, naphthalene amine such as 1,5-diaminonaphthalene; heterocyclic aromatic diamine such as 2,6-diaminopyridine, 2,4-diaminopyridine, 2,4-diamino-S-triazine; 4,4′- Diaminobiphenyl, 4,4'-diaminodiphenylmethane, 4,4 '-(9-fluoreni Den) -dianiline, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 2,2′-dichloro-4,4 '-Diaminobiphenyl, 2,2', 5,5'-tetrachlorobenzidine, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2- Bis (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) ) Benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl 4,4'-bis (3-aminophenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] Aromatic diamines such as -1,1,1,3,3,3-hexafluoropropane, 4,4′-diaminodiphenylthioether, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, etc. However, it is not limited to these. The diamine containing a C—F bond includes 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 2,2-bis (4-aminophenyl) -1,1,1, Examples include 3,3,3-hexafluoropropane and 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane.

  As the weight average molecular weight (Mw) of the polyimide used in the present invention, a dimethylformamide solution (10 mM lithium bromide and 10 mM phosphoric acid was added to make a 1 L dimethylformamide solution) was used as a developing solvent. A polyethylene oxide standard having a weight average molecular weight (Mw) of 20,000 to 300,000 is preferably used. More preferably, it is 50,000-200,000, Most preferably, it is 70,000-180,000. If it is said range, the polymer film which has as a main component the polyimide excellent in mechanical strength can be obtained.

  Although there is no restriction | limiting in particular as the imidation ratio of the said polyimide, What is 90% or more is used preferably. More preferably, it is 95% or more, and particularly preferably 98% or more. The imidation ratio can be determined from a peak integral intensity ratio between a proton peak derived from polyamic acid, which is a polyimide precursor, and a proton peak derived from polyimide, in a nuclear magnetic resonance (NMR) spectrum.

  The retardation film used for the second optical element is obtained by, for example, defoaming a polyimide solution (dope) obtained by dissolving a resin composition containing polyimide, additives and the like in a solvent, an endless stainless belt rotating drum, a polymer film ( For example, it can be obtained by uniformly casting a thin film on the surface of a substrate (also referred to as a support) such as a PET film and evaporating the solvent.

  The total solid content concentration of the polyimide solution varies depending on solubility, coating viscosity, wettability, thickness after coating, etc., but in order to obtain a polyimide layer with high surface uniformity, Those in which 2 to 100 (weight ratio) are dissolved are preferably used. More preferably, solid content is 10-50 (weight ratio) with respect to the solvent 100, Most preferably, it is 20-40 (weight ratio). If it is said range, it can be thin and can form the polyimide layer excellent in surface uniformity and optical uniformity.

  Although there is no restriction | limiting in particular as said solvent, The liquid substance which melt | dissolves the said polyimide uniformly and makes it a solution is used preferably. Cyclopentanone, cyclohexanone, methyl isobutyl ketone, toluene, ethyl acetate, dichloromethane, chloroform and tetrahydrofuran are preferred. With these solvents, a retardation film having good optical uniformity can be obtained.

  Although there is no restriction | limiting in particular as a viscosity of the said polyimide solution, The value measured by the shear rate 1000 (1 / s) in 23 degreeC is 50-600 (mPa * s) normally, It is used preferably. More preferably, it is 100-300 (mPa * s), Most preferably, it is 120-200 (mPa * s). If it is said range, it is thin and can form the retardation film excellent in surface uniformity and optical uniformity.

  There is no restriction | limiting in particular as a method of coating the said polyimide solution on the surface of a base material, The coating system using a conventionally well-known coater can be used. The types of coaters used in the above coating methods include reverse roll coaters, forward rotating roll coaters, gravure coaters, knife coaters, rod coaters, slot orifice coaters, curtain coaters, fountain coaters, air doctor coaters, kiss coaters, dip coaters, and bead coaters. , Blade coater, cast coater, spray coater, spin coater, extrusion coater, hot melt coater and the like. Among these, a reverse roll coater, a normal rotation roll coater, a gravure coater, a rod coater, a slot orifice coater, a curtain coater, and a fountain coater are preferably used in the present invention. If it is a coating method using the above-mentioned coater, a thin polyimide layer having excellent surface uniformity and optical uniformity can be formed.

  The means for drying the polyimide solution is not particularly limited, but is an air circulation type constant temperature oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, a roll heated for temperature control, a heat pipe roll. Alternatively, a known heating method or temperature control method using a metal belt can be used.

  The drying temperature of the polyimide solution is usually preferably 50 ° C to 250 ° C. More preferably, it is 80 degreeC-150 degreeC. Further, the drying may be performed at a constant temperature, or may be performed while increasing or decreasing the temperature stepwise. As a specific example of stepwise drying, for example, primary drying is performed at a temperature of 40 ° C to 140 ° C (preferably 40 ° C to 120 ° C), and then 150 ° C to 250 ° C (preferably 150 ° C to 180 ° C). ), A two-stage drying process in which secondary drying is performed. By performing the stepwise drying treatment as described above, a polyimide layer having further excellent smoothness can be formed.

  Although there is no restriction | limiting in particular as drying time of the said polyimide solution, In order to obtain the polyimide layer excellent in surface uniformity, it is 1 minute-20 minutes, for example, More preferably, it is 1 minute-15 minutes, Especially preferably 2 to 10 minutes.

  An example of a method for producing a retardation film used for the second optical element will be described with reference to FIG. FIG. 8 is a schematic diagram showing the concept of a typical production process of a retardation film used for the second optical element. For example, an isotropic film is fed out from the feeding unit 401 as a base material, and a polyimide solution is applied to the surface of the isotropic film in the coater unit 402. The isotropic film coated with the polyimide solution is sent to drying means 403, 404, and 405, and the solvent is evaporated to form a laminated film 406 having a polyimide layer and an isotropic film layer. The laminated film 406 is wound around the winding unit 407.

  The amount of residual volatile components in the polymer film containing polyimide as a main component is not particularly limited. Is more than 0 and 3% or less. The amount of residual volatile components of the polyimide layer can be determined from the amount of weight loss before and after heating when heated at 250 ° C. for 10 minutes.

  In addition to the above-described retardation film used for the second optical element, a commercially available optical film can be used as it is. Further, a commercially available optical film may be used after being subjected to secondary processing such as stretching / relaxation. Examples of commercially available polymer films that exhibit optically negative uniaxiality include “Fujitac Series” manufactured by Fuji Photo Film Co., Ltd.

F. Isotropic film In the present specification, “isotropic film” means a film that has a small optical difference depending on the direction in three dimensions and does not substantially exhibit anisotropic optical properties such as birefringence. Say. Specifically, the refractive index distribution satisfies nx = ny = nz where the in-plane main refractive index is nx, ny, and the refractive index in the thickness direction is nz. In the present specification, nx, ny and nz include not only the case where they are completely the same, but also the case where nx, ny and nz are substantially the same. Here, “when nx, ny and nz are substantially the same” includes, for example, a case where Re [590] is 10 nm or less and Rth [590] is 10 nm or less.

  Any appropriate method can be adopted as a method of obtaining the isotropic film. For example, an appropriate one can be appropriately selected from compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, solvent casting, and the like. Among these molding methods, the extrusion molding method or the solvent casting method is particularly preferable. This is because the smoothness of the resulting isotropic film can be improved and good optical uniformity (for example, a retardation value that is small in the plane and in the thickness direction) can be obtained.

  The thickness of the isotropic film can be appropriately selected according to the purpose. The thickness is preferably 20 μm to 200 μm, more preferably 20 μm to 180 μm, and particularly preferably 20 μm to 150 μm. If it is said range, the optical film excellent in mechanical strength and optical uniformity can be obtained.

The absolute value (C [590] (m ² / N)) of the photoelastic coefficient of the isotropic film is preferably 1 × 10 ^{−12 to} 100 × 10 ⁻¹² , more preferably 1 × 10 ^−12. a to 50 × 10 ^-12, particularly preferably from ^{1 × 10 -12 ~30 × 10 -12} , and most preferably ^{1 × 10 -12 ~8 × 10 -12} . The smaller the absolute value of the photoelastic coefficient, the less the retardation and unevenness of the retardation due to the contraction stress of the polarizer and the heat of the backlight when used in a liquid crystal display device. A display device can be obtained.

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

  As the material for forming the isotropic film, a material excellent in transparency, mechanical strength, thermal stability, moisture shielding, etc. is preferably used. Of these, cellulose ester, cycloolefin resin obtained by hydrogenating a ring-opening polymer of norbornene monomer, norbornene monomer, and α-olefin monomer are preferable in that the absolute value of the photoelastic coefficient is further small. An addition copolymer and a polymer film containing as a main component at least one resin selected from an addition copolymer of a maleimide monomer and an olefin monomer.

  Any appropriate cellulose ester can be adopted as the cellulose ester. Specific examples include organic acid esters such as cellulose acetate, cellulose propionate, and cellulose butyrate. The cellulose ester may be, for example, a mixed organic acid ester in which a part of the hydroxyl group of cellulose is substituted with an acetyl group and a propionyl group. In order to obtain a polymer film containing the cellulose ester as a main component and having both Re [590] and Rth [590] being small, it is preferably formed by a casting method, and Re [590] and Rth [590] can be appropriately adjusted depending on molding conditions, film thickness, and the like. The film can be obtained, for example, by the method described in Example 1 of JP-A-7-112446. In addition, a commercially available film can be obtained by reducing Rth [590] before the treatment by swelling it with a ketone solvent such as cyclopentanone and then performing a drying treatment.

  As the cycloolefin-based resin obtained by hydrogenating the ring-opening polymer of the norbornene-based monomer, an appropriate one can be appropriately selected from the same as described in the above section D-4. In order to obtain a polymer film containing as a main component a cycloolefin resin obtained by hydrogenating the ring-opening polymer of the norbornene monomer, and having both Re [590] and Rth [590] small, extrusion molding Preferably, Re [590] and Rth [590] can be appropriately adjusted depending on molding conditions, film thickness, and the like. Specifically, for example, the film can be obtained by the method described in Example 1 of JP-A-4-301415.

  The addition copolymer of the norbornene monomer and the α-olefin monomer can be obtained, for example, by the method described in Example 1 of JP-A No. 61-292601. The norbornene-based monomer is as described in the above section E-4. The α-olefin monomer has 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms. For example, ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3- Examples thereof include methyl-1-pentene, 4-methyl-1-pentene, 1-hexane, 1-octane, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecane and 1-icosene. Among these, ethylene is particularly preferable. These α-olefin monomers can be used alone or in combination of two or more. Further, if necessary, other vinyl monomers can be copolymerized within a range not impairing the object of the present invention. In order to obtain a polymer film containing as a main component an addition copolymer of the above norbornene monomer and α-olefin monomer and having both Re [590] and Rth [590] small, it is molded by an extrusion molding method. It is preferable that Re [590] and Rth [590] can be appropriately adjusted depending on molding conditions, film thickness, and the like.

  The addition copolymer of maleimide monomer and olefin monomer used for the isotropic film can be obtained, for example, by the method described in Example 1 of JP-A-5-59193. Examples of the maleimide monomer include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, Ni-butylmaleimide, Ns-butyl. Maleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide, N-cyclo N-alkyl-substituted maleimides such as propylmaleimide, N-cyclobutylmaleimide, and N-cyclohexylmaleimide, among which N-methylmaleimide, N-ethylmaleimide, Ni-propylmaleimide, and N-cyclohexylmaleimide are preferable. Moreover, these can be used 1 type or in combination of 2 or more types. Examples of the olefin monomer include isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 1-methyl-1-heptene, 1-isooctene, 2-methyl-1- It is an olefin monomer such as octene, 2-ethyl-1-pentene, 2-methyl-2-butene, 2-methyl-2-pentene, 2-methyl-2-hexene, and among these, isobutene is particularly preferable. These olefin monomers can be used alone or in combination of two or more. Further, if necessary, other vinyl monomers can be copolymerized within a range not impairing the object of the present invention. In order to obtain a polymer film containing as a main component an addition copolymer of the maleimide monomer and the olefin monomer and having both small Re [590] and Rth [590], it is molded by an extrusion molding method. Preferably, Re [590] and Rth [590] can be appropriately adjusted depending on molding conditions, film thickness, and the like. The film can be obtained, for example, by the method described in Example 1 of JP-A-2004-45893.

  As the isotropic film, in addition to the above-mentioned materials, a polycarbonate-based resin having 9,9-bis (4-hydroxyphenyl) fluorene as a side difference described in JP-A-2001-253960, ) NTS publication "Development and application technology of optical polymer material" 2003 edition p. 194-p. A random copolymer of the monomer constituting the polymer exhibiting positive orientation birefringence described in 207 and the monomer constituting the polymer exhibiting negative orientation birefringence, or an anisotropic low molecule or birefringent crystal is doped. The polymer etc. which were made can be illustrated.

G. Liquid crystal display device The liquid crystal panel of the present invention is a liquid crystal display device such as a personal computer, a liquid crystal television, a mobile phone, a personal digital assistant (PDA), an organic electroluminescence display (organic EL), a projector, a projection television, a plasma television, etc. It can be used for an image display device. Especially, the polarizing element and liquid crystal panel of this invention are used suitably for a liquid crystal display device, and are used especially suitably for a liquid crystal television.

  FIG. 9 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. The liquid crystal display device 150 includes a liquid crystal panel 100 of the present invention, protective layers 60 and 60 ′ disposed on both sides of the liquid crystal panel 100, and a surface treatment layer 70 disposed on the outer side of the protective layers 60 and 60 ′. 70 ′, and a brightness enhancement film 80, a prism sheet 110, a light guide plate 120, and a lamp 130 disposed on the outer side (backlight side) of the surface treatment layer 70 ′. As the surface treatment layers 70 and 70 ′, treatment layers subjected to hard coat treatment, antireflection treatment, antisticking treatment, diffusion treatment (also referred to as antiglare treatment), and the like are used. Moreover, as the said brightness improvement film 80, the polarization separation film (Example: Sumitomo 3M Co., Ltd. brand name "D-BEF series") etc. which have a polarization selection layer are used. By using these optical members, a display device with higher display characteristics can be obtained. Moreover, in another embodiment, as long as the optical member illustrated in FIG. 9 satisfies the present invention, a part of the optical member is omitted depending on the driving mode and application of the liquid crystal cell used, or others. The optical member can be replaced.

  The contrast ratio (YW / YB) in the azimuth angle 45 ° direction and the polar angle 60 ° direction of the liquid crystal display device provided with the liquid crystal panel of the present invention is preferably 10 to 150, more preferably 20 to 150, particularly. Preferably it is 50-150.

  Further, the color shift amount (Δab value) in the azimuth angle 45 ° direction and polar angle 60 ° direction of the liquid crystal display device is preferably 0.05 to 0.39, more preferably 0.05 to 0.30. Yes, particularly preferably 0.05 to 0.25.

The present invention will be further described using the above examples and comparative examples. In addition, this invention is not limited only to these Examples. In addition, each analysis method used in the Example is as follows.
(1) Measuring method of single transmittance and polarization degree of polarizer:
It measured at 23 degreeC using the spectrophotometer [Murakami Color Research Laboratory Co., Ltd. product name "DOT-3"].
(2) Method for measuring molecular weight of cycloolefin resin obtained by hydrogenating a ring-opening polymer of norbornene monomer:
Polystyrene was calculated as a standard sample by the gel permeation chromatograph (GPC) method. Specifically, it measured with the following apparatuses, instruments, and measurement conditions.
・ Analyzer: “HLC-8120GPC” manufactured by TOSOH
Column: TSKgel Super HM-H / H4000 / H3000 / H2000
Column size: 6.0 mmI. D. × 150mm
-Eluent: Tetrahydrofuran-Flow rate: 0.6 ml / min.
・ Detector: RI
-Column temperature: 40 ° C
・ Injection volume: 20 μl
(3) Method for measuring molecular weight of polyimide:
Polyethylene oxide was calculated as a standard sample by a gel permeation chromatograph (GPC) method. Specifically, it measured with the following apparatuses, instruments, and measurement conditions.
Sample: A sample was dissolved in an eluent to prepare a 0.1 wt% solution.
Pretreatment: left for 8 hours and filtered through a 0.45 μm membrane filter.
・ Analyzer: “HLC-8020GPC” manufactured by Tosoh Corporation
・ Column: Tosoh GMH _XL + GMH _XL + G2500H _XL
Column size: 7.8 mmφ x 30 cm each (total 90 cm)
Eluent: Dimethylformamide (added with 10 mM lithium bromide and 10 mM phosphoric acid to make up to 1 L dimethylformamide solution)
-Flow rate: 0.8 ml / min.
・ Detector: RI (differential refractometer)
-Column temperature: 40 ° C
・ Injection volume: 100 μl
(4) Measuring method of thickness:
When the thickness was less than 10 μm, measurement was performed using a thin film spectrophotometer [manufactured by Otsuka Electronics Co., Ltd., “instant multiphotometry system MCPD-2000”]. When the thickness was 10 μm or more, measurement was performed using an Anritsu digital micrometer “KC-351C type”.
(5) Measuring method of phase difference values (Re, Rth):
It measured with the light of wavelength 590nm in 23 degreeC using the phase difference meter [Oji Scientific Instruments Co., Ltd. product name "KOBRA21-ADH"] based on a parallel Nicol rotation method. For wavelength dispersion measurement, light having a wavelength of 480 nm was also used.
(6) Measuring method of average refractive index of film:
It calculated | required from the refractive index measured with the light of wavelength 589nm in 23 degreeC using the Abbe refractometer [The product name "DR-M4" by Atago Co., Ltd.].
(7) Transmittance measurement method:
It measured with the light of wavelength 590nm in 23 degreeC using the ultraviolet visible spectrophotometer [The product name "V-560" by JASCO Corporation].
(8) Measuring method of photoelastic coefficient:
Using a spectroscopic ellipsometer [product name “M-220” manufactured by JASCO Corporation], the sample (size 2 cm × 10 cm) is sandwiched at both ends and stress (5 to 15 N) is applied to the phase difference at the center of the sample. The value (23 ° C./wavelength 590 nm) was measured and calculated from the slope of the function of stress and retardation value.
(9) Measuring method of contrast ratio of liquid crystal display device:
The following method, a liquid crystal cell [made by Matsushita Electric Industrial Co., Ltd., 32V type TH-32LX10], and a measuring device are used to turn on the backlight in a dark room at 23 ° C. After the lapse of time, measurement was performed. A white image and a black image were displayed on the liquid crystal display device, and the Y value of the XYZ display system in the azimuth angle 45 ° direction and polar angle 60 ° direction of the display screen was measured by a product name “EZ Contrast 160D” manufactured by ELDIM. Then, the contrast ratio “YW / YB” in the oblique direction was calculated from the Y value (YW) in the white image and the Y value (YB) in the black image. An azimuth angle of 45 ° represents an azimuth rotated 45 ° counterclockwise when the long side of the panel is 0 °, and a polar angle of 60 ° is when the front direction of the display screen is 0 °. Represents a direction inclined at an angle of 60 °.
(10) Measuring method of color shift amount of liquid crystal display device:
The following method, a liquid crystal cell [made by Matsushita Electric Industrial Co., Ltd., 32V type TH-32LX10], and a measuring device are used to turn on the backlight in a dark room at 23 ° C. After the lapse of time, measurement was performed. A black image was displayed on the liquid crystal display device, and the hue, a value, and b value in all directions (360 °) in the polar angle 60 ° direction were measured using a product name “EZ Contrast 160D” manufactured by ELDIM. The average values of the a value and b value in all directions in the polar angle 60 ° direction are a _ave. Value and b _ave. Value, respectively, and the a value and b value in the polar angle 60 ° azimuth angle 45 ° are respectively a _The values were ₄₅ ° and b ₄₅ °. The color shift amount (Δab value) in the oblique direction was calculated from the following formula: [(a ₄₅ ° −a _ave. ) ² + (b ₄₅ ° −b _ave. ) ² ] ^1/2 . Note that the azimuth angle 45 ° represents an azimuth rotated 45 ° counterclockwise when the long side of the panel is 0 °. Further, the polar angle of 60 ° represents an orientation viewed obliquely by 60 ° when the vertical direction is 0 ° with respect to the panel.
(11) Photographing the luminance distribution of the display screen of the liquid crystal display device:
Measurement was performed in a dark room at 23 ° C. using the following method, a liquid crystal cell [mounted on Matsushita Electric Industrial Co., Ltd., 32V type TH-32LX10], and a measuring device. Using a two-dimensional color distribution measuring apparatus “CA-1500” manufactured by Minolta Co., Ltd., the display screen was photographed after a predetermined time had elapsed since the backlight was turned on.

Production of Polarizer [Reference Example 1]
Polymer film mainly composed of polyvinyl alcohol [Kuraray Co., Ltd., trade name “9P75R (thickness: 75 μm, average polymerization degree: 2,400, saponification degree 99.9 mol%)”] at 30 ° C. ± 3 ° C. In a dyeing bath containing iodine and potassium iodide held, the film was uniaxially stretched 2.5 times while dyeing using a roll stretching machine. Subsequently, it was uniaxially stretched so as to be 6 times the original length of the polyvinyl alcohol film while performing a crosslinking reaction in an aqueous solution containing boric acid and potassium iodide maintained at 60 ± 3 ° C. The obtained film was dried in an air-circulating constant temperature oven at 50 ° C. ± 1 ° C. for 30 minutes to obtain a polarizer P1 having a moisture content of 26%, a thickness of 28 μm, a degree of polarization of 99.9%, and a unit transmittance of 43.5%. And P2.

Preparation of isotropic film [Reference Example 2]
Polymer film mainly composed of cycloolefin resin obtained by hydrogenating a ring-opening polymer of norbornene monomer having a thickness of 100 μm [trade name “Zeonor ZF14-100” manufactured by Nippon Zeon Co., Ltd. (average refractive index = 1.51) )] Was used as is to make an isotropic film 1-A. The characteristics of the obtained isotropic film 1-A are shown in Table 1 below together with the film characteristics of Reference Examples 3 to 5 described later.

[Reference Example 3]
65 parts by weight of a copolymer comprising isobutene and N-methylmaleimide (N-methylmaleimide content 50 mol%, glass transition temperature 157 ° C.), acrylonitrile / styrene copolymer (AS resin) (acrylonitrile content 27 mol) %) 35 parts by weight and 1 part by weight of 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol (ultraviolet absorber) After being dried at 100 ° C. for 5 hours, the pellets were extruded at 270 ° C. using a 40 nm φ single screw extruder and a 400 mm wide T-die, and the sheet-like molten resin was cooled with a cooling drum to a width of about 600 mm. A polymer film (average refractive index = 1.51) having a thickness of 40 μm was produced. This polymer film was designated as isotropic film 1-B. Table 1 shows the properties of the obtained isotropic film 1-B.

[Reference Example 4]
A solution prepared by adding 20 parts by weight of cycloolefin resin [trade name “ARTON” manufactured by JSR Co., Ltd.] obtained by hydrogenating a ring-opening polymer of a pelleted norbornene monomer to 80 parts by weight of cyclopentanone, Polymer film mainly composed of triacetyl cellulose having a thickness of 80 μm [trade name “UZ-TAC” manufactured by Fuji Photo Film Co., Ltd. (average refractive index = 1.48, Re [590] = 0.8 nm, Rth [590] ] = 60.5 nm)] was applied at a coating thickness of 150 μm, and the polymer film was swollen and then dried at 140 ° C. for 3 minutes. After drying, the cycloolefin resin film formed on the surface of the polymer film was peeled off to produce a polymer film containing transparent triacetyl cellulose as a main component. This polymer film was designated as isotropic film 1-C. The characteristics of the obtained isotropic film 1-C are shown in Table 1.

Production of retardation film used for first optical element [Reference Example 5]
Polymer film mainly composed of cycloolefin resin obtained by hydrogenating a ring-opening polymer of norbornene monomer having a thickness of 100 μm [trade name “Zeonor ZF14-100” manufactured by Nippon Zeon Co., Ltd. (average refractive index = 1.51) , Re [590] = 2.0 nm, Rth [590] = 8.0 nm)] on both sides of a biaxially stretched polypropylene film [trade name “Trefan E60-high shrinkage type” (thickness 60 μm) manufactured by Toray Industries, Inc. ] Was bonded through an acrylic pressure-sensitive adhesive layer (thickness: 15 μm). After that, the film was held in the longitudinal direction with a roll stretching machine and stretched 1.38 times in an air circulation drying oven (measured at a distance of 3 cm from the film backside) at 146 ° C. ± 1 ° C. Phase difference film 2-A was produced. The properties of the obtained retardation film 2-A are shown in Table 2 below together with the film properties of Reference Examples 6 to 9 described later.

  The biaxially stretched polypropylene film used in this example (Reference Example 5) had a shrinkage rate at 140 ° C. of 6.4% in the MD direction and 12.8% in the TD direction. The acrylic pressure-sensitive adhesive uses isononyl acrylate (weight average molecular weight = 550,000) synthesized by solution polymerization as a base polymer. A product obtained by mixing 3 parts by weight of a trade name “Coronate L” manufactured by Co., Ltd. and 10 parts by weight of a catalyst [trade name “OL-1” manufactured by Tokyo Fine Chemical Co., Ltd.] was used.

[Reference Example 6]
A retardation film 2-B was produced in the same manner as in Reference Example 5, except that the stretching temperature was changed to 148 ° C. instead of 146 ° C., and the stretching ratio was changed to 1.40 times instead of 1.38 times. Table 2 shows the properties of the obtained retardation film 2-B.

[Reference Example 7]
A retardation film 2-C was produced in the same manner as in Reference Example 5, except that the stretching temperature was changed to 148 ° C. instead of 146 ° C., and the stretching ratio was changed to 1.35 times instead of 1.38 times. Table 2 shows the properties of the obtained retardation film 2-C.

[Reference Example 8]
Polymer film mainly composed of cycloolefin resin obtained by hydrogenating a ring-opening polymer of norbornene monomer having a thickness of 40 μm [trade name “Zeonor ZF14-40” manufactured by Nippon Zeon Co., Ltd. (average refractive index = 1.51) , Re [590] = 1.0 nm, Rth [590] = 3.0 nm)] on both sides of the biaxially stretched polypropylene film [trade name “Trefan E60-high shrinkage type” (thickness 60 μm) manufactured by Toray Industries, Inc. ] Was bonded through an acrylic pressure-sensitive adhesive layer (thickness: 15 μm). After that, the film is held in the longitudinal direction with a roll stretching machine and stretched 1.62 times in an air circulation drying oven (measured at a distance of 3 cm from the film back surface) at 143 ° C. ± 1 ° C. Phase difference film 2-D was produced. Table 2 shows the properties of the obtained retardation film 2-D.

[Reference Example 9]
Polymer film containing 55 μm-thick polycarbonate resin (weight average molecular weight 60,000) and styrene resin (weight average molecular weight 1,300) [trade name “Elmec PF film” manufactured by Kaneka Corporation (average refractive index = 1.55, Re [590] = 5.0 nm, Rth [590] = 12.0 nm)] on both sides of a biaxially stretched polypropylene film [trade name “Treffan E60-low shrinkage type” manufactured by Toray Industries, Inc.] (Thickness 60 μm)] was bonded through an acrylic pressure-sensitive adhesive layer (thickness 15 μm). After that, the film was held in the longitudinal direction with a roll stretching machine and stretched 1.27 times in an air circulation type drying oven (measured at a distance of 3 cm from the film back surface) at 147 ° C. ± 1 ° C. Phase difference film 2-E was produced. Table 2 shows the properties of the obtained retardation film 2-E.

  The biaxially stretched polypropylene film used in this example (Reference Example 9) had a shrinkage rate at 140 ° C. of 5.7% in the MD direction and 7.6% in the TD direction. The same acrylic adhesive as in Reference Example 5 was used.

Example of polyimide synthesis [Reference Example 10]
2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride in a reaction vessel (500 mL) equipped with a mechanical stirrer, Dean-Stark device, nitrogen inlet tube, thermometer and condenser tube [Clariant Japan Co., Ltd.] 17.77 g (40 mmol) and 2,2-bis (trifluoromethyl) -4,4′-diaminobiphenyl [Wakayama Seika Kogyo Co., Ltd.] 12.81 g (40 mmol) added. Subsequently, a solution in which 2.58 g (20 mmol) of isoquinoline was dissolved in 275.21 g of m-cresol was added, and the mixture was stirred at 23 ° C. for 1 hour (600 rpm) to obtain a uniform solution. Next, the reaction vessel was heated using an oil bath so that the temperature in the reaction vessel became 180 ± 3 ° C., and stirred for 5 hours while maintaining the temperature to obtain a yellow solution. After further stirring for 3 hours, the heating and stirring were stopped, and the mixture was allowed to cool to room temperature.

  Acetone was added to the yellow solution in the reaction vessel to completely dissolve the gel to prepare a diluted solution (7% by weight). When this diluted solution was gradually added to 2 L of isopropyl alcohol while stirring, a white powder was precipitated. This powder was collected by filtration and poured into 1.5 L of isopropyl alcohol for washing. Further, the same operation was repeated once again for washing, and then the powder was again collected by filtration. This was dried in a 60 ° C. air circulation type constant temperature oven for 48 hours and then dried at 150 ° C. for 7 hours to obtain a polyimide composed of repeating units represented by the following formula (1) as a white powder (yield 85 %). The polyimide had a polymerization average molecular weight (Mw) of 124,000 and an imidation ratio of 99.9%.

  A polyimide solution (15% by weight) obtained by dissolving the above polyimide in methyl isobutyl ketone was applied to the surface of a polyethylene terephthalate film [trade name Lumirror S27-E, manufactured by Toray Industries, Inc.] in one direction with a rod coater. It was dried for 5 minutes in an air circulation type thermostatic oven at 1 ° C. to form a polyimide layer having a thickness of 3 μm on the triacetyl cellulose film. When this polyimide layer was peeled and the optical characteristics were measured, the transmittance was 90%, the average refractive index was 1.55, Rth [590] was 125 nm, and Δnxz was 0.04.

Production of second optical element [Reference Example 11]
17.7 parts by weight of the polyimide (white powder) obtained in Reference Example 10 was dissolved in 100 parts by weight of methyl isobutyl ketone (boiling point 116 ° C.) to prepare a 15% by weight polyimide solution. This polyimide solution was applied to the surface of the isotropic film 1-B obtained in Reference Example 3 in one direction with a rod coater. Next, the solvent is evaporated by drying in a 135 ± 1 ° C. air circulating constant temperature oven for 5 minutes, and then in a 150 ± 1 ° C. air circulating constant temperature oven for 10 minutes, and a 7.0 μm thick polyimide layer ( A laminated film (total thickness 47 μm) having a residual volatile component amount of 2% was prepared. This laminated film (comprising a retardation film and an isotropic film) was designated as a second optical element 3-A. The characteristics of the obtained second optical element 3-A are shown in Table 3 below together with film characteristics of Reference Examples 12 to 13 described later.

[Reference Example 12]
2,2'-dichloro-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride (40 mmol) and 2,2-bis (trifluoromethyl) -4,4'-diaminobiphenyl (40 mmol) Was used as a starting material (monomer) and a polyimide [weight average molecular weight = 94,000, average refractive index = 1.57, Δnxz = 0.07] was synthesized in the same manner as in Reference Example 10. Using this polyimide, a laminated film (total thickness 44 μm) provided with a polyimide layer having a thickness of 4.0 μm was produced in the same manner as in Reference Example 11. This laminated film was designated as a second optical element 3-B. Table 3 shows the characteristics of the obtained second optical element 3-B. Further, in order to evaluate the smoothness of the laminated film, the laminated film was sandwiched between two polarizers whose absorption axes were orthogonal to each other, and visually observed from an oblique direction in the light of a backlight (see FIG. 10 (a)), no unevenness was observed and the smoothness was good.

[Reference Example 13]
2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride (40 mmol), 2,2-bis (trifluoromethyl) -4,4′-diaminobiphenyl (20 mmol), 3,3′-Diaminodiphenylsulfone (20 mmol) was used as a starting material (monomer), and polyimide [weight average molecular weight = 71,000, average refractive index = 1.55, Δnxz = 0. 02] was synthesized. Using this polyimide, a laminated film (total thickness 54 μm) having a polyimide layer having a thickness of 14.0 μm was produced in the same manner as in Reference Example 11. This laminated film was designated as a second optical element 3-C. Table 3 shows the characteristic properties of the obtained second optical element 3-C. Further, in order to evaluate the smoothness of the laminated film, the laminated film was sandwiched between two polarizers whose absorption axes were orthogonal to each other, and visually observed from an oblique direction in the light of a backlight (see FIG. 10 (b)), unevenness was observed.

Preparation of VA mode liquid crystal cell [Reference Example 14]
A liquid crystal panel is taken out from a liquid crystal display device [32V type TH-32LX10 manufactured by Matsushita Electric Industrial Co., Ltd.] including a VA mode liquid crystal cell, and the polarizing plate and the retardation film disposed above and below the liquid crystal cell are removed. The glass surface (front and back) of the liquid crystal cell was washed. When no electric field was applied to the liquid crystal cell, Rth [590] was 310 nm, and R40 [480] / R40 [590] was 1.1.

Production of liquid crystal panel and liquid crystal display device [Example 1]
The retardation film 2-A obtained in Reference Example 5 is used as the first optical element on the viewing side surface of the liquid crystal cell obtained in Reference Example 14, and the long side of the liquid crystal cell and the retardation film 2-A are used. It laminated | stacked through the acrylic adhesive layer (thickness 20 micrometers) so that a slow axis might become mutually parallel. Next, on the surface of the retardation film 2-A, the polarizer P1 obtained in Reference Example 1 is parallel to the long side of the liquid crystal cell and the absorption axis of the polarizer P1 (at this time, the retardation film 2-A). An adhesive layer composed mainly of a modified polyvinyl alcohol having an acetoacetyl group so that the slow axis of A and the absorption axis of the polarizer P1 are parallel to each other (0 ° ± 0.5 °) Thickness 1 μm) [Nippon Synthetic Chemical Co., Ltd., trade name “Gosefimmer Z200”].

  Subsequently, the second optical element 3-B obtained in Reference Example 12 is placed on the backlight side of the liquid crystal cell so that the isotropic film 1-B is on the liquid crystal cell side. Lamination was performed via an acrylic pressure-sensitive adhesive layer (thickness 20 μm) so that the short side and the slow axis of the second optical element 3-B were parallel to each other. Next, the polarizer P2 obtained in Reference Example 1 is parallel to the surface of the second optical element 3-B in which the short side of the liquid crystal cell and the absorption axis of the polarizer P2 are parallel (at this time, the polarizer P1 And an absorption axis of the polarizer P2 are laminated via an acrylic pressure-sensitive adhesive layer (thickness 20 μm) so that they are orthogonal to each other (90 ° ± 0.5 °). In addition, on the outer side (the side far from the liquid crystal cell) of the polarizers P1 and P2, as a protective layer, a polymer film mainly composed of a commercially available cellulose ester of 80 μm [trade name “UZ- manufactured by Fuji Photo Film Co., Ltd.] TAC ”] was laminated via an adhesive layer (thickness 1 μm) mainly composed of a modified polyvinyl alcohol having an acetoacetyl group (trade name“ Goseifamer Z200 ”manufactured by Nippon Synthetic Chemical Co., Ltd.).

  The liquid crystal panel A thus obtained was combined with a backlight unit to prepare a liquid crystal display device A. The liquid crystal panel immediately after turning on the backlight had good display uniformity over the entire surface. The contrast ratio in the oblique direction and the color shift amount in the oblique direction were measured 10 minutes after the backlight was turned on. The obtained characteristics are shown in Table 4.

  Further, after the pack light was turned on for 10 hours, the display screen of the liquid crystal display device was photographed in a dark room using a two-dimensional color distribution measuring device “CA-1500” manufactured by Minolta Co., Ltd. As a result, as shown in FIG. 11, display unevenness due to the heat of the backlight was hardly observed.

[Example 2]
A liquid crystal panel B and a liquid crystal display device B were produced in the same manner as in Example 1 except that the retardation film 2-C obtained in Reference Example 7 was used as the first optical element. The liquid crystal panel immediately after turning on the backlight had good display uniformity over the entire surface. The contrast ratio in the oblique direction and the color shift amount in the oblique direction were measured 10 minutes after the backlight was turned on. The obtained characteristics are shown in Table 4. Further, after the pack light was turned on for 10 hours, the display screen of the liquid crystal display device was photographed in a dark room using a two-dimensional color distribution measuring device “CA-1500” manufactured by Minolta Co., Ltd. As a result, display unevenness due to the heat of the backlight was hardly observed.

[Example 3]
As the first optical element, two retardation films 2-D obtained in Reference Example 8 were used (laminated using an acrylic adhesive having a thickness of 20 μm so that the slow axes of the respective retardation films were parallel to each other). Except for the above, a liquid crystal panel C and a liquid crystal display device C were produced in the same manner as in Example 1. The liquid crystal panel immediately after turning on the backlight had good display uniformity over the entire surface. The contrast ratio in the oblique direction and the color shift amount in the oblique direction were measured 10 minutes after the backlight was turned on. The obtained characteristics are shown in Table 4. Further, after the pack light was turned on for 10 hours, the display screen of the liquid crystal display device was photographed in a dark room using a two-dimensional color distribution measuring device “CA-1500” manufactured by Minolta Co., Ltd. As a result, display unevenness due to the heat of the backlight was hardly observed.

[Comparative Example 1]
A liquid crystal panel D and a liquid crystal display device D were produced in the same manner as in Example 1 except that the retardation film 2-E obtained in Reference Example 9 was used as the first optical element. The liquid crystal panel immediately after turning on the backlight had good display uniformity over the entire surface. The contrast ratio in the oblique direction and the color shift amount in the oblique direction were measured 10 minutes after the backlight was turned on. The obtained characteristics are shown in Table 4. Further, after the pack light was turned on for 10 hours, the display screen of the liquid crystal display device was photographed in a dark room using a two-dimensional color distribution measuring device “CA-1500” manufactured by Minolta Co., Ltd. As a result, as shown in FIG. 12, the display unevenness due to the heat of the backlight was so large as to adversely affect the display of characters and images.

[Comparative Example 2]
Example 1 except that the retardation film 2-E obtained in Reference Example 9 was used as the first optical element and the second optical element 3-A obtained in Reference Example 11 was used. A liquid crystal panel E and a liquid crystal display device E were produced by the same method. The liquid crystal panel immediately after turning on the backlight had good display uniformity over the entire surface. The contrast ratio in the oblique direction and the color shift amount in the oblique direction were measured 10 minutes after the backlight was turned on. The obtained characteristics are shown in Table 4. Further, after the pack light was turned on for 10 hours, the display screen of the liquid crystal display device was photographed in a dark room using a two-dimensional color distribution measuring device “CA-1500” manufactured by Minolta Co., Ltd. As a result, as shown in FIG. 13, the display unevenness due to the heat of the backlight was so great as to have a serious adverse effect on the display of characters and images.

[Evaluation]
As shown in Examples 1 to 3, a ring-opening polymer of a norbornene monomer is hydrogenated on one surface of a liquid crystal cell including a liquid crystal layer containing a nematic liquid crystal aligned in a homeotropic alignment in the absence of an electric field. A first optical element including a stretched polymer film composed mainly of a cycloolefin-based resin is disposed, and a second optically negative uniaxial property is provided on the other surface of the liquid crystal cell. The liquid crystal panel in which the optical element is arranged has a higher contrast ratio in the oblique direction than the liquid crystal panel using the polymer film of the aromatic resin as the first optical element shown in Comparative Examples 1 and 2, and The amount of color shift in the oblique direction could be reduced. In addition, the liquid crystal display device incorporating the liquid crystal panel of the present invention prevents the shift and unevenness of the retardation value due to the contraction stress of the polarizer and the heat of the backlight even when the backlight is lit for a long time, and provides good display uniformity. A liquid crystal panel and a liquid crystal display device having the property were able to be obtained. Factors that have produced such a great effect are: (1) a material having a small photoelastic coefficient and a phase difference that actually has a relationship of nx>nz> ny and satisfies a specific phase difference value; It is mentioned that a film was produced. In addition, the wavelength dispersion characteristic of the optical element is set to an appropriate value, (3) the retardation film used for the second optical element is made thin with a material having a large birefringence in the thickness direction, and (4) the first It is considered that the chromatic dispersion characteristic of the optical element 2 is set to an appropriate value, which is useful for the manifestation of the effect of the present invention.

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

It is a schematic sectional drawing of the liquid crystal panel by preferable embodiment of this invention. It is a schematic perspective view of the liquid crystal panel of FIG. It is a schematic diagram which shows the concept of the typical manufacturing process of the polarizer used for this invention. It is a schematic perspective view explaining the typical example of preferable embodiment of a 1st optical element including the relationship with the absorption axis of a polarizer. It is a schematic diagram which shows the concept of the typical manufacturing process of the phase difference film used for a 1st optical element. It is a typical conceptual diagram explaining the method of canceling the phase difference value of a liquid crystal cell using a 2nd optical element. It is a schematic perspective view explaining the typical example of preferable embodiment of a 2nd optical element including the relationship with the absorption axis of a polarizer. It is a schematic diagram which shows the concept of the typical manufacturing process of the phase difference film used for a 2nd optical element. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. It is the photograph which evaluated the smoothness of the laminated film used for a 2nd optical element. It is a photograph which shows the measurement result of the display nonuniformity of the liquid crystal panel by Example 1 of this invention. It is a photograph which shows the measurement result of the display nonuniformity of the liquid crystal panel by the comparative example 1 of this invention. It is a photograph which shows the measurement result of the display nonuniformity of the liquid crystal panel by the comparative example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal cell 21, 22 Polarizer 30 1st polarizer 31, 33, 34 Retardation film 32, 42 Isotropic film 40 2nd polarizer 41, 43, 44 Retardation film 60, 60 'Protective layer 70 , 70 ′ Surface treatment layer 80 Brightness enhancement film 100 Liquid crystal panel 110 Prism sheet 120 Light guide plate 130 Lamp 150 Liquid crystal display device 200 Feeding section 210 Iodine aqueous solution bath 211, 212, 221, 222, 231, 232 Roll 220 Boric acid and iodide Bath 240 of aqueous solution containing potassium Drying means 260 Winding parts 307, 308 Laminating rolls 301, 303, 305 Feeding parts 304, 306 Shrinkable film 309 Temperature control means 310, 311, 312, 313 Rolls 314, 316, 319 Winding Picker 401 Feeder 402 Coater 403, 404, 405 Drying means 407 Winding unit

Claims (7)

A liquid crystal cell including a liquid crystal layer including nematic liquid crystal aligned in a homeotropic alignment in the absence of an electric field, a polarizer disposed on both sides of the liquid crystal cell, one of the polarizers, and the liquid crystal cell; A first optical element disposed between, and a second optical element disposed between the other of the polarizers and the liquid crystal cell,
The first optical element satisfies the following formulas (1) and (2), and is a stretched polymer film mainly composed of a cycloolefin resin obtained by hydrogenating a ring-opening polymer of a norbornene monomer. Including
A liquid crystal panel in which the second optical element has substantially optically negative uniaxiality:
200 nm ≦ Re [590] ≦ 350 nm (1)
0 nm <Rth [590] <Re [590] (2)
However, Re [590] and Rth [590] are an in-plane retardation value and a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C., respectively.   2. The liquid crystal panel according to claim 1, wherein a slow axis of the first optical element is substantially parallel or orthogonal to an absorption axis of one of the polarizers. The liquid crystal panel according to claim 1 or 2, wherein the second optical element satisfies the following formulas (3) and (4):
0 nm ≦ Re [590] ≦ 10 nm (3)
100 nm ≦ Rth [590] ≦ 800 nm (4)
However, Re [590] and Rth [590] are an in-plane retardation value and a thickness direction retardation value measured with light having a wavelength of 590 nm at 23 ° C., respectively.   The second optical element includes a retardation film in which a difference between an in-plane main refractive index (nx) and a refractive index (nz) in a thickness direction is 0.03 to 0.20. A liquid crystal panel according to any one of the above.   The liquid crystal panel according to claim 4, wherein the retardation film is a polymer film containing polyimide as a main component.   A liquid crystal television comprising the liquid crystal panel according to claim 1. A liquid crystal display device comprising the liquid crystal panel according to claim 1.